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 error.
Signed-off-by: Per Forlin <per.forlin@xxxxxxxxxx>
---
drivers/mmc/core/core.c | 6 ++++++
include/linux/mmc/host.h | 3 +++
2 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 91a0a74..542aa06 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -279,8 +279,14 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
mmc_wait_for_req_done(host, host->areq->mrq);
err = host->areq->err_check(host->card, host->areq);
if (err) {
+ /* post process the completed failed request */
mmc_post_req(host, host->areq->mrq, 0);
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);
host->areq = NULL;
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 1d09562..7896fb4 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -108,6 +108,9 @@ struct mmc_host_ops {
* It is optional for the host to implement pre_req and post_req in
* order to support double buffering of requests (prepare one
* 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,
int err);
--
1.7.4.1
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