mmc: core: clarify how to use post_req in case of errors
The err condition in post_req() is set to undo a call made to pre_req() that hasn't been started yet. The err condition is not set if an MMC request returns an error. Signed-off-by: Per Forlin <per.forlin@linaro.org> Acked-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Chris Ball <cjb@laptop.org>
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@ -320,8 +320,14 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
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mmc_wait_for_req_done(host, host->areq->mrq);
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err = host->areq->err_check(host->card, host->areq);
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if (err) {
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/* post process the completed failed request */
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mmc_post_req(host, host->areq->mrq, 0);
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if (areq)
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/*
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* Cancel the new prepared request, because
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* it can't run until the failed
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* request has been properly handled.
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*/
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mmc_post_req(host, areq->mrq, -EINVAL);
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host->areq = NULL;
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@ -109,6 +109,9 @@ struct mmc_host_ops {
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* It is optional for the host to implement pre_req and post_req in
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* order to support double buffering of requests (prepare one
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* request while another request is active).
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* pre_req() must always be followed by a post_req().
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* To undo a call made to pre_req(), call post_req() with
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* a nonzero err condition.
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*/
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void (*post_req)(struct mmc_host *host, struct mmc_request *req,
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int err);
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