Re: [PATCH 2/4 v4] MMC/SD: Add callback function to detect card

[Aaron Lu <aaron.lu@amd.com>]

On Fri, Jan 13, 2012 at 07:05:19AM +0000, Huang Changming-R66093 wrote:
> If you read the previous email about this serial patches discussed with other guys, you can understand.
> 
> > -----Original Message-----
> > From: Aaron Lu [mailto:aaron.lu@amd.com]
> > Sent: Friday, January 13, 2012 2:28 PM
> > To: Huang Changming-R66093
> > Cc: linux-mmc@vger.kernel.org; Chris Ball
> > Subject: Re: [PATCH 2/4 v4] MMC/SD: Add callback function to detect card
> > 
> > Hi,
> > 
> > On Fri, Jan 13, 2012 at 04:52:42AM +0000, Huang Changming-R66093 wrote:
> > >
> > > > For sd hosts, this should only happen for hosts which have
> > > > SDHCI_QUIRK_BROKEN_CARD_DETECTION set.
> > > Yes, but which will impact the performance.
> > 
> > You only set this bit when your host broke, and if your host has other
> > means to detect this, then go with your newly added callback.
> To detect the card state, if SDHCI_QUIRK_BROKEN_CARD_DETECTION is set, then driver will send command to card, which will cause the bad performance.
> So my patch will do:
> 1. use get_cd to detect the card state, if platform don't support this feature(get_cd is not defined in special platform), -ENOSYS will be returned
> 2. if -ENOSYS, then send the command to card.

OK, this is clear. I didn't know there is a get_cd callback already
defined in sdhci_ops with a clear return value description, sorry for
the mess.

> > I just suggested to change the name and use a different return value for
> > this get_cd function, not to add a new function call.
> > 
> The description for get_cd in file "include/linux/mmc/host.h":
>          * 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
> I don't think your suggest is reasonable.
Agree.