[PATCH] SPI core tweaks, bugfix
This includes various updates to the SPI core:
- Fixes a driver model refcount bug in spi_unregister_master() paths.
- The spi_master structures now have wrappers which help keep drivers
from needing class-level get/put for device data or for refcounts.
- Check for a few setup errors that would cause oopsing later.
- Docs say more about memory management. Highlights the use of DMA-safe
i/o buffers, and zero-initializing spi_message and such metadata.
- Provide a simple alloc/free for spi_message and its spi_transfer;
this is only one of the possible memory management policies.
Nothing to break code that already works.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
David Brownell
Greg Kroah-Hartman
Родитель
b885244eb2
Коммит
0c868461fc
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@ -363,6 +363,22 @@ upper boundaries might include sysfs (especially for sensor readings),
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the input layer, ALSA, networking, MTD, the character device framework,
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or other Linux subsystems.
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Note that there are two types of memory your driver must manage as part
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of interacting with SPI devices.
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- I/O buffers use the usual Linux rules, and must be DMA-safe.
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You'd normally allocate them from the heap or free page pool.
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Don't use the stack, or anything that's declared "static".
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- The spi_message and spi_transfer metadata used to glue those
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I/O buffers into a group of protocol transactions. These can
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be allocated anywhere it's convenient, including as part of
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other allocate-once driver data structures. Zero-init these.
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If you like, spi_message_alloc() and spi_message_free() convenience
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routines are available to allocate and zero-initialize an spi_message
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with several transfers.
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How do I write an "SPI Master Controller Driver"?
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-------------------------------------------------
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@ -38,7 +38,7 @@ static void spidev_release(struct device *dev)
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if (spi->master->cleanup)
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spi->master->cleanup(spi);
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class_device_put(&spi->master->cdev);
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spi_master_put(spi->master);
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kfree(dev);
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}
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@ -90,7 +90,7 @@ static int spi_suspend(struct device *dev, pm_message_t message)
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int value;
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struct spi_driver *drv = to_spi_driver(dev->driver);
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if (!drv || !drv->suspend)
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if (!drv->suspend)
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return 0;
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/* suspend will stop irqs and dma; no more i/o */
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@ -105,7 +105,7 @@ static int spi_resume(struct device *dev)
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int value;
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struct spi_driver *drv = to_spi_driver(dev->driver);
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if (!drv || !drv->resume)
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if (!drv->resume)
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return 0;
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/* resume may restart the i/o queue */
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@ -198,7 +198,7 @@ spi_new_device(struct spi_master *master, struct spi_board_info *chip)
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/* NOTE: caller did any chip->bus_num checks necessary */
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if (!class_device_get(&master->cdev))
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if (!spi_master_get(master))
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return NULL;
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proxy = kzalloc(sizeof *proxy, GFP_KERNEL);
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@ -244,7 +244,7 @@ spi_new_device(struct spi_master *master, struct spi_board_info *chip)
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return proxy;
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fail:
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class_device_put(&master->cdev);
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spi_master_put(master);
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kfree(proxy);
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return NULL;
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}
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@ -324,8 +324,6 @@ static void spi_master_release(struct class_device *cdev)
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struct spi_master *master;
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master = container_of(cdev, struct spi_master, cdev);
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put_device(master->cdev.dev);
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master->cdev.dev = NULL;
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kfree(master);
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}
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@ -339,8 +337,9 @@ static struct class spi_master_class = {
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/**
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* spi_alloc_master - allocate SPI master controller
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* @dev: the controller, possibly using the platform_bus
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* @size: how much driver-private data to preallocate; a pointer to this
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* memory in the class_data field of the returned class_device
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* @size: how much driver-private data to preallocate; the pointer to this
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* memory is in the class_data field of the returned class_device,
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* accessible with spi_master_get_devdata().
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*
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* This call is used only by SPI master controller drivers, which are the
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* only ones directly touching chip registers. It's how they allocate
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@ -350,14 +349,17 @@ static struct class spi_master_class = {
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* master structure on success, else NULL.
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*
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* The caller is responsible for assigning the bus number and initializing
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* the master's methods before calling spi_add_master(), or else (on error)
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* calling class_device_put() to prevent a memory leak.
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* the master's methods before calling spi_add_master(); and (after errors
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* adding the device) calling spi_master_put() to prevent a memory leak.
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*/
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struct spi_master * __init_or_module
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spi_alloc_master(struct device *dev, unsigned size)
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{
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struct spi_master *master;
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if (!dev)
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return NULL;
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master = kzalloc(size + sizeof *master, SLAB_KERNEL);
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if (!master)
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return NULL;
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@ -365,7 +367,7 @@ spi_alloc_master(struct device *dev, unsigned size)
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class_device_initialize(&master->cdev);
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master->cdev.class = &spi_master_class;
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master->cdev.dev = get_device(dev);
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class_set_devdata(&master->cdev, &master[1]);
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spi_master_set_devdata(master, &master[1]);
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return master;
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}
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@ -387,6 +389,8 @@ EXPORT_SYMBOL_GPL(spi_alloc_master);
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*
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* This must be called from context that can sleep. It returns zero on
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* success, else a negative error code (dropping the master's refcount).
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* After a successful return, the caller is responsible for calling
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* spi_unregister_master().
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*/
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int __init_or_module
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spi_register_master(struct spi_master *master)
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@ -396,6 +400,9 @@ spi_register_master(struct spi_master *master)
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int status = -ENODEV;
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int dynamic = 0;
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if (!dev)
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return -ENODEV;
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/* convention: dynamically assigned bus IDs count down from the max */
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if (master->bus_num == 0) {
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master->bus_num = atomic_dec_return(&dyn_bus_id);
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@ -425,7 +432,7 @@ EXPORT_SYMBOL_GPL(spi_register_master);
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static int __unregister(struct device *dev, void *unused)
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{
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/* note: before about 2.6.14-rc1 this would corrupt memory: */
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device_unregister(dev);
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spi_unregister_device(to_spi_device(dev));
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return 0;
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}
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@ -440,8 +447,9 @@ static int __unregister(struct device *dev, void *unused)
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*/
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void spi_unregister_master(struct spi_master *master)
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{
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class_device_unregister(&master->cdev);
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(void) device_for_each_child(master->cdev.dev, NULL, __unregister);
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class_device_unregister(&master->cdev);
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master->cdev.dev = NULL;
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}
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EXPORT_SYMBOL_GPL(spi_unregister_master);
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@ -487,6 +495,9 @@ EXPORT_SYMBOL_GPL(spi_busnum_to_master);
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* by leaving it selected in anticipation that the next message will go
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* to the same chip. (That may increase power usage.)
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*
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* Also, the caller is guaranteeing that the memory associated with the
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* message will not be freed before this call returns.
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*
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* The return value is a negative error code if the message could not be
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* submitted, else zero. When the value is zero, then message->status is
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* also defined: it's the completion code for the transfer, either zero
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@ -524,9 +535,9 @@ static u8 *buf;
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* is zero for success, else a negative errno status code.
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* This call may only be used from a context that may sleep.
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*
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* Parameters to this routine are always copied using a small buffer,
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* large transfers should use use spi_{async,sync}() calls with
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* dma-safe buffers.
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* Parameters to this routine are always copied using a small buffer;
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* performance-sensitive or bulk transfer code should instead use
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* spi_{async,sync}() calls with dma-safe buffers.
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*/
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int spi_write_then_read(struct spi_device *spi,
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const u8 *txbuf, unsigned n_tx,
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@ -60,8 +60,8 @@ struct spi_device {
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u8 mode;
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#define SPI_CPHA 0x01 /* clock phase */
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#define SPI_CPOL 0x02 /* clock polarity */
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#define SPI_MODE_0 (0|0)
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#define SPI_MODE_1 (0|SPI_CPHA) /* (original MicroWire) */
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#define SPI_MODE_0 (0|0) /* (original MicroWire) */
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#define SPI_MODE_1 (0|SPI_CPHA)
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#define SPI_MODE_2 (SPI_CPOL|0)
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#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA)
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#define SPI_CS_HIGH 0x04 /* chipselect active high? */
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@ -209,6 +209,30 @@ struct spi_master {
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void (*cleanup)(const struct spi_device *spi);
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};
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static inline void *spi_master_get_devdata(struct spi_master *master)
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{
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return class_get_devdata(&master->cdev);
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}
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static inline void spi_master_set_devdata(struct spi_master *master, void *data)
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{
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class_set_devdata(&master->cdev, data);
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}
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static inline struct spi_master *spi_master_get(struct spi_master *master)
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{
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if (!master || !class_device_get(&master->cdev))
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return NULL;
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return master;
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}
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static inline void spi_master_put(struct spi_master *master)
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{
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if (master)
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class_device_put(&master->cdev);
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}
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/* the spi driver core manages memory for the spi_master classdev */
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extern struct spi_master *
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spi_alloc_master(struct device *host, unsigned size);
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@ -271,11 +295,17 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum);
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* stay selected until the next transfer. This is purely a performance
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* hint; the controller driver may need to select a different device
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* for the next message.
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*
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* The code that submits an spi_message (and its spi_transfers)
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* to the lower layers is responsible for managing its memory.
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* Zero-initialize every field you don't set up explicitly, to
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* insulate against future API updates.
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*/
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struct spi_transfer {
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/* it's ok if tx_buf == rx_buf (right?)
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* for MicroWire, one buffer must be null
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* buffers must work with dma_*map_single() calls
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* buffers must work with dma_*map_single() calls, unless
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* spi_message.is_dma_mapped reports a pre-existing mapping
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*/
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const void *tx_buf;
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void *rx_buf;
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@ -302,6 +332,11 @@ struct spi_transfer {
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* @status: zero for success, else negative errno
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* @queue: for use by whichever driver currently owns the message
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* @state: for use by whichever driver currently owns the message
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*
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* The code that submits an spi_message (and its spi_transfers)
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* to the lower layers is responsible for managing its memory.
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* Zero-initialize every field you don't set up explicitly, to
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* insulate against future API updates.
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*/
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struct spi_message {
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struct spi_transfer *transfers;
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@ -336,6 +371,29 @@ struct spi_message {
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void *state;
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};
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/* It's fine to embed message and transaction structures in other data
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* structures so long as you don't free them while they're in use.
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*/
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static inline struct spi_message *spi_message_alloc(unsigned ntrans, gfp_t flags)
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{
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struct spi_message *m;
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m = kzalloc(sizeof(struct spi_message)
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+ ntrans * sizeof(struct spi_transfer),
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flags);
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if (m) {
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m->transfers = (void *)(m + 1);
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m->n_transfer = ntrans;
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}
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return m;
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}
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static inline void spi_message_free(struct spi_message *m)
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{
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kfree(m);
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}
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/**
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* spi_setup -- setup SPI mode and clock rate
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* @spi: the device whose settings are being modified
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@ -363,7 +421,10 @@ spi_setup(struct spi_device *spi)
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* The completion callback is invoked in a context which can't sleep.
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* Before that invocation, the value of message->status is undefined.
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* When the callback is issued, message->status holds either zero (to
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* indicate complete success) or a negative error code.
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* indicate complete success) or a negative error code. After that
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* callback returns, the driver which issued the transfer request may
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* deallocate the associated memory; it's no longer in use by any SPI
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* core or controller driver code.
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*
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* Note that although all messages to a spi_device are handled in
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* FIFO order, messages may go to different devices in other orders.
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@ -445,6 +506,7 @@ spi_read(struct spi_device *spi, u8 *buf, size_t len)
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return spi_sync(spi, &m);
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}
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/* this copies txbuf and rxbuf data; for small transfers only! */
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extern int spi_write_then_read(struct spi_device *spi,
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const u8 *txbuf, unsigned n_tx,
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u8 *rxbuf, unsigned n_rx);
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@ -555,8 +617,9 @@ spi_register_board_info(struct spi_board_info const *info, unsigned n)
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/* If you're hotplugging an adapter with devices (parport, usb, etc)
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* use spi_new_device() to describe each device. You would then call
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* spi_unregister_device() to start making that device vanish.
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* use spi_new_device() to describe each device. You can also call
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* spi_unregister_device() to start making that device vanish, but
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* normally that would be handled by spi_unregister_master().
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*/
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extern struct spi_device *
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spi_new_device(struct spi_master *, struct spi_board_info *);
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