linux-kernel - RE: [PATCH] mmc: sd: Add a variable to check a faulty device

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Date: Fri, 16 Feb 2024 11:26:38 +0900
From: 이승희 <sh043.lee@...sung.com>
To: "'Greg KH'" <gregkh@...uxfoundation.org>
Cc: "'Ulf Hansson'" <ulf.hansson@...aro.org>, <linux-mmc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <avri.altman@....com>,
	<grant.jung@...sung.com>, <jt77.jang@...sung.com>,
	<dh0421.hwang@...sung.com>, <junwoo80.lee@...sung.com>,
	<jangsub.yi@...sung.com>, <cw9316.lee@...sung.com>,
	<sh8267.baek@...sung.com>, <wkon.kim@...sung.com>, <sh043.lee@...sung.com>
Subject: RE: [PATCH] mmc: sd: Add a variable to check a faulty device

> -----Original Message-----
> On Thu, Feb 15, 2024 at 08:15:45PM +0900, 이승희 wrote:
> > > Subject: Re: [PATCH] mmc: sd: Add a variable to check a faulty
> > > device
> 
> Does this really belong in the body of the email?  You might want a nicer
> email client :)
> 

It was caused by unfamiliarity with upstream. Sorry for the inconvenience.

> > > > The variable's usage is expected to be used through the sysfs node
> > > > in
> > > the vendor module.
> > >
> > > What "vendor module"?  You need to include all of the needed code
> > > here please.
> > >
> > > thanks,
> > >
> > > greg k-h
> >
> > This only purpose of this variable is to identify a faulty card on host
> side.
> >
> > In the past, we can identify that the card is inserted or not with
> reading get_cd() function.
> > But now, most mobile devices use hybrid type of SD card tray.
> > If the tray is inserted, the return value of get_cd is the same whatever
> the SD card is inserted or not.
> > It can help us diagonose the status of a SD card as well.
> >
> > Here is the example of usage.
> >
> > static ssize_t status_show(struct device *dev,
> >                 struct device_attribute *attr, char *buf) {
> >         struct mmc_host *host = dev_get_drvdata(dev);
> >         struct mmc_card *card = host->card;
> >         char *status = NULL;
> >
> >         if (card)
> >                 status = mmc_card_readonly(card) ? "PERMWP" : "NORMAL";
> >         else
> >                 status = host->init_failed ? "INITFAIL" : "NOCARD";
> >
> >         return sysfs_emit(buf, "%s\n", status); }
> 
> What will userspace do with this information?
> 
> And why isn't this part of the patch you submitted?
> 
> > As for the sysfs node, it should keep the path of node with or without
> the SD card.
> > That's why I mention the vendor module.
> 
> What vendor module?  What do you mean by vendor module?  You know we can't
> add code to the kernel that is only used by code that is NOT in our kernel
> tree.  You don't want us to take stuff like that, so why is it being
> proposed here?
> 
> confused,
> 
> greg k-h

We need to inform users that there is a problem with the SD card.
There is a diagnostic tool in the customer service app,
Adding a sysfs node is under consideration so that the tool can diagnose the SD card.
To do this, a node capable of diagnosing an SD card is needed regardless of whether an SD card is present or not.

Since I understand that the proposed sysfs node is difficult to apply to the kernel, no separate commit was posted.
So, I created this PR because I needed a variable to identify the faulty device.

I will consider this part again.
And if you have any other good ideas, please feel free to suggest them.

Thank you for your review.
Seunghui Lee.