178 строки
6.6 KiB
C
178 строки
6.6 KiB
C
/*D:300
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* The Guest console driver
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*
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* This is a trivial console driver: we use lguest's DMA mechanism to send
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* bytes out, and register a DMA buffer to receive bytes in. It is assumed to
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* be present and available from the very beginning of boot.
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*
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* Writing console drivers is one of the few remaining Dark Arts in Linux.
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* Fortunately for us, the path of virtual consoles has been well-trodden by
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* the PowerPC folks, who wrote "hvc_console.c" to generically support any
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* virtual console. We use that infrastructure which only requires us to write
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* the basic put_chars and get_chars functions and call the right register
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* functions.
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:*/
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/*M:002 The console can be flooded: while the Guest is processing input the
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* Host can send more. Buffering in the Host could alleviate this, but it is a
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* difficult problem in general. :*/
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/* Copyright (C) 2006 Rusty Russell, IBM Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/lguest_bus.h>
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#include <asm/paravirt.h>
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#include "hvc_console.h"
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/*D:340 This is our single console input buffer, with associated "struct
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* lguest_dma" referring to it. Note the 0-terminated length array, and the
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* use of physical address for the buffer itself. */
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static char inbuf[256];
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static struct lguest_dma cons_input = { .used_len = 0,
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.addr[0] = __pa(inbuf),
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.len[0] = sizeof(inbuf),
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.len[1] = 0 };
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/*D:310 The put_chars() callback is pretty straightforward.
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*
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* First we put the pointer and length in a "struct lguest_dma": we only have
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* one pointer, so we set the second length to 0. Then we use SEND_DMA to send
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* the data to (Host) buffers attached to the console key. Usually a device's
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* key is a physical address within the device's memory, but because the
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* console device doesn't have any associated physical memory, we use the
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* LGUEST_CONSOLE_DMA_KEY constant (aka 0). */
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static int put_chars(u32 vtermno, const char *buf, int count)
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{
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struct lguest_dma dma;
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/* FIXME: DMA buffers in a "struct lguest_dma" are not allowed
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* to go over page boundaries. This never seems to happen,
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* but if it did we'd need to fix this code. */
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dma.len[0] = count;
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dma.len[1] = 0;
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dma.addr[0] = __pa(buf);
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lguest_send_dma(LGUEST_CONSOLE_DMA_KEY, &dma);
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/* We're expected to return the amount of data we wrote: all of it. */
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return count;
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}
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/*D:350 get_chars() is the callback from the hvc_console infrastructure when
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* an interrupt is received.
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*
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* Firstly we see if our buffer has been filled: if not, we return. The rest
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* of the code deals with the fact that the hvc_console() infrastructure only
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* asks us for 16 bytes at a time. We keep a "cons_offset" variable for
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* partially-read buffers. */
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static int get_chars(u32 vtermno, char *buf, int count)
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{
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static int cons_offset;
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/* Nothing left to see here... */
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if (!cons_input.used_len)
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return 0;
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/* You want more than we have to give? Well, try wanting less! */
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if (cons_input.used_len - cons_offset < count)
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count = cons_input.used_len - cons_offset;
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/* Copy across to their buffer and increment offset. */
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memcpy(buf, inbuf + cons_offset, count);
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cons_offset += count;
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/* Finished? Zero offset, and reset cons_input so Host will use it
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* again. */
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if (cons_offset == cons_input.used_len) {
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cons_offset = 0;
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cons_input.used_len = 0;
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}
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return count;
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}
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/*:*/
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static struct hv_ops lguest_cons = {
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.get_chars = get_chars,
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.put_chars = put_chars,
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};
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/*D:320 Console drivers are initialized very early so boot messages can go
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* out. At this stage, the console is output-only. Our driver checks we're a
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* Guest, and if so hands hvc_instantiate() the console number (0), priority
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* (0), and the struct hv_ops containing the put_chars() function. */
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static int __init cons_init(void)
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{
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if (strcmp(paravirt_ops.name, "lguest") != 0)
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return 0;
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return hvc_instantiate(0, 0, &lguest_cons);
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}
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console_initcall(cons_init);
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/*D:370 To set up and manage our virtual console, we call hvc_alloc() and
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* stash the result in the private pointer of the "struct lguest_device".
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* Since we never remove the console device we never need this pointer again,
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* but using ->private is considered good form, and you never know who's going
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* to copy your driver.
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*
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* Once the console is set up, we bind our input buffer ready for input. */
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static int lguestcons_probe(struct lguest_device *lgdev)
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{
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int err;
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/* The first argument of hvc_alloc() is the virtual console number, so
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* we use zero. The second argument is the interrupt number.
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*
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* The third argument is a "struct hv_ops" containing the put_chars()
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* and get_chars() pointers. The final argument is the output buffer
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* size: we use 256 and expect the Host to have room for us to send
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* that much. */
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lgdev->private = hvc_alloc(0, lgdev_irq(lgdev), &lguest_cons, 256);
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if (IS_ERR(lgdev->private))
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return PTR_ERR(lgdev->private);
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/* We bind a single DMA buffer at key LGUEST_CONSOLE_DMA_KEY.
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* "cons_input" is that statically-initialized global DMA buffer we saw
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* above, and we also give the interrupt we want. */
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err = lguest_bind_dma(LGUEST_CONSOLE_DMA_KEY, &cons_input, 1,
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lgdev_irq(lgdev));
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if (err)
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printk("lguest console: failed to bind buffer.\n");
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return err;
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}
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/* Note the use of lgdev_irq() for the interrupt number. We tell hvc_alloc()
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* to expect input when this interrupt is triggered, and then tell
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* lguest_bind_dma() that is the interrupt to send us when input comes in. */
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/*D:360 From now on the console driver follows standard Guest driver form:
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* register_lguest_driver() registers the device type and probe function, and
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* the probe function sets up the device.
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*
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* The standard "struct lguest_driver": */
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static struct lguest_driver lguestcons_drv = {
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.name = "lguestcons",
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.owner = THIS_MODULE,
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.device_type = LGUEST_DEVICE_T_CONSOLE,
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.probe = lguestcons_probe,
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};
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/* The standard init function */
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static int __init hvc_lguest_init(void)
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{
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return register_lguest_driver(&lguestcons_drv);
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}
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module_init(hvc_lguest_init);
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