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mmc: core: clarify how to use post_req in case of errors

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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>
This commit is contained in:
Per Forlin 2011-08-29 15:35:58 +02:00 • committed by Chris Ball
commit 7c8a2829c2
2 changed files with 9 additions and 0 deletions
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6
drivers/mmc/core/core.c
View file

@ -320,8 +320,14 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
mmc_wait_for_req_done(host, host->areq->mrq); mmc_wait_for_req_done(host, host->areq->mrq);
err = host->areq->err_check(host->card, host->areq); err = host->areq->err_check(host->card, host->areq);
if (err) { if (err) {
/* post process the completed failed request */
mmc_post_req(host, host->areq->mrq, 0); mmc_post_req(host, host->areq->mrq, 0);
if (areq) if (areq)
/*
* Cancel the new prepared request, because
* it can't run until the failed
* request has been properly handled.
*/
mmc_post_req(host, areq->mrq, -EINVAL); mmc_post_req(host, areq->mrq, -EINVAL);
host->areq = NULL; host->areq = NULL;

3
include/linux/mmc/host.h
View file

@ -109,6 +109,9 @@ struct mmc_host_ops {
* It is optional for the host to implement pre_req and post_req in * It is optional for the host to implement pre_req and post_req in
* order to support double buffering of requests (prepare one * order to support double buffering of requests (prepare one
* request while another request is active). * request while another request is active).
* pre_req() must always be followed by a post_req().
* To undo a call made to pre_req(), call post_req() with
* a nonzero err condition.
*/ */
void (*post_req)(struct mmc_host *host, struct mmc_request *req, void (*post_req)(struct mmc_host *host, struct mmc_request *req,
int err); int err);