Commit 93b6911a authored by Wolfram Sang's avatar Wolfram Sang Committed by Ulf Hansson
Browse files

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



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

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 148634d2

include/linux/mmc/host.h

+21 −10
Original line number Diff line number Diff line
@@ -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);