Re: [PATCH 3/3] MMC/SD: add callback function to detect card

[Adrian Hunter <adrian.hunter@nokia.com>]

Adrian Hunter wrote:
> Matt Fleming wrote:
>> On Fri, Aug 27, 2010 at 08:05:13PM +0100, Chris Ball wrote:
>>> Hi,
>>>
>>> On Fri, Dec 04, 2009 at 03:55:09PM +0800, r66093@freescale.com wrote:
>>>> From: Jerry Huang <Chang-Ming.Huang@freescale.com>
>>>>
>>>> Add callback function to check if the card has been removed.
>>>>
>>>> in order to check if the card has been removed, the function mmc_send_status will send commad CMD13 to card and ask the card to send its status register to driver, which will generate interrupt repeatly and make the system bad.
>>>> Therefore, get_cd callback is used to detect the card if the driver has.
>>>>
>>>> Signed-off-by: Jerry Huang <Chang-Ming.Huang@freescale.com>
>>>> ---
>>>>  drivers/mmc/core/mmc.c |    5 ++++-
>>>>  drivers/mmc/core/sd.c  |    5 ++++-
>>>>  2 files changed, 8 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>>>> index 06084db..c5c676d 100644
>>>> --- a/drivers/mmc/core/mmc.c
>>>> +++ b/drivers/mmc/core/mmc.c
>>>> @@ -494,7 +494,10 @@ static void mmc_detect(struct mmc_host *host)
>>>>  	/*
>>>>  	 * Just check if our card has been removed.
>>>>  	 */
>>>> -	err = mmc_send_status(host->card, NULL);
>>>> +	if (host->ops->get_cd)
>>>> +		err = !host->ops->get_cd(host);
>>>> +	else
>>>> +		err = mmc_send_status(host->card, NULL);
>>>>  
>>>>  	mmc_release_host(host);
>>>>  
>>>> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
>>>> index cd81c39..3cf1f38 100644
>>>> --- a/drivers/mmc/core/sd.c
>>>> +++ b/drivers/mmc/core/sd.c
>>>> @@ -548,7 +548,10 @@ static void mmc_sd_detect(struct mmc_host *host)
>>>>  	/*
>>>>  	 * Just check if our card has been removed.
>>>>  	 */
>>>> -	err = mmc_send_status(host->card, NULL);
>>>> +	if (host->ops->get_cd)
>>>> +		err = !host->ops->get_cd(host);
>>>> +	else
>>>> +		err = mmc_send_status(host->card, NULL);
>>>>  
>>>>  	mmc_release_host(host);
>>>>  
>>>> -- 
>>>> 1.6.4
>>> This patchset wasn't replied to -- any comments on it from the list?
>> I think this change makes sense, although it needs to be a bit smarter
>> with error handling because the get_cd() functions can return -ENOSYS if
>> they are not implemented (but the function pointer is still valid).
>>
>> 	int err = 0;
>>
>> 	if (host->ops->get_cd) {
>> 		err = host->ops->get_cd(host);
>> 		if (err >= 0)
>> 			err = !err;
>> 	}
>>
>> 	if (!host->ops->get_cd || err < 0)
>> 		err = mmc_send_status(host->card, NULL);
>>
>> Thoughts?
> 
> I am not sure it won't cause problems.
> 
> If you change the card then card detect will return true because
> there is a card but send status will fail because the card is not
> initialised.  So the two do not seem equivalent.

But maybe the following?

	int err = 0;

	if (host->ops->get_cd)
		err = !host->ops->get_cd(host);

	if (!err)
		err = mmc_send_status(host->card, NULL);



> 
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> 
>