[PATCH v2 18/20] mmc: sdio: enable a default power off mode of the card

On Sun, 25 Jul 2010, Ohad Ben-Cohen wrote:

On Thu, Jul 22, 2010 at 2:35 PM, Roger Quadros [off-list ref] wrote:

quoted

On 07/21/2010 08:33 PM, ext Ohad Ben-Cohen wrote:

quoted

Add support for an SDIO device to stay powered off even without
the presence of an SDIO function driver. A host should explicitly
ask for it by means of MMC_CAP_DONT_POWER_CARD, and the SDIO
function driver should know it needs to call sdio_claim_power
before accessing the device.

Signed-off-by: Ohad Ben-Cohen<redacted>

Shouldn't this be the default behaviour? If there is no function driver for
any of the functions of the card, then sdio core shold power off the card.

I don't see a need for a special capability flag for this.

in fact MMC_CAP_DONT_POWER_CARD does not seem like an mmc host's capability

Totally agree.

I didn't want to change the current behavior of the cards/funcs so I
looked for a way to explicitly power down only specific cards.

Alternatively we could power down all cards at the end
mmc_attach_sdio, and then power them up selectively in sdio_bus_probe,
just before calling probe. If the probe succeeds, the function driver
takes over. If the probe fails, we can power them down again.

Exactly!

Is that what you meant ?

This would work both if the sdio function driver is already loaded, or
will only be loaded at a later time. But I'm not too fond of the extra
power on/off cycles that it will introduce for each card..

This is still way better than introducing knowledge about specific cards 
in the host drivers.


Nicolas