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mmc: host: add note that set_ios needs to handle 0Hz properly

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While here, refactor the comments so that they are before the
declaration they are referring to.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Wolfram Sang 2016-04-01 17:44:36 +02:00 committed by Ulf Hansson
parent 148634d24d
commit 93b6911ac1
1 changed files with 21 additions and 10 deletions
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31
include/linux/mmc/host.h
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@ -93,28 +93,39 @@ struct mmc_host_ops {
void (*pre_req)(struct mmc_host *host, struct mmc_request *req,
bool is_first_req);
void (*request)(struct mmc_host *host, struct mmc_request *req);
/*
* Avoid calling the next three functions too often or in a "fast
* path", since underlaying controller might implement them in an
* expensive and/or slow way. Also note that these functions might
* sleep, so don't call them in the atomic contexts!
*/
/*
* Notes to the set_ios callback:
* ios->clock might be 0. For some controllers, setting 0Hz
* as any other frequency works. However, some controllers
* explicitly need to disable the clock. Otherwise e.g. voltage
* switching might fail because the SDCLK is not really quiet.
*/
void (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
/*
* Avoid calling these three functions too often or in a "fast path",
* since underlaying controller might implement them in an expensive
* and/or slow way.
*
* Also note that these functions might sleep, so don't call them
* in the atomic contexts!
*
* Return values for the get_ro callback should be:
* 0 for a read/write card
* 1 for a read-only card
* -ENOSYS when not supported (equal to NULL callback)
* or a negative errno value when something bad happened
*
*/
int (*get_ro)(struct mmc_host *host);
/*
* Return values for the get_cd callback should be:
* 0 for a absent card
* 1 for a present card
* -ENOSYS when not supported (equal to NULL callback)
* or a negative errno value when something bad happened
*/
void (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
int (*get_ro)(struct mmc_host *host);
int (*get_cd)(struct mmc_host *host);
void (*enable_sdio_irq)(struct mmc_host *host, int enable);