Re: [PATCH v1] mtd: core: add sysfs nodes for querying the flash name and id

From: Boris Brezillon <boris.brezillon@collabora.com>
To: Zhuohao Lee <zhuohao@chromium.org>
Cc: "Nicolas Boichat" <drinkcat@chromium.org>,
	"Vignesh Raghavendra" <vigneshr@ti.com>,
	bbrezillon@kernel.org, richard@nod.at,
	"Brian Norris" <briannorris@chromium.org>,
	"Marek Vašut" <marek.vasut@gmail.com>,
	linux-mtd@lists.infradead.org,
	"Brian Norris" <computersforpeace@gmail.com>,
	"David Woodhouse" <dwmw2@infradead.org>
Subject: Re: [PATCH v1] mtd: core: add sysfs nodes for querying the flash name and id
Date: Tue, 2 Apr 2019 14:01:41 +0200	[thread overview]
Message-ID: <20190402140141.385a79d8@collabora.com> (raw)
In-Reply-To: <CABD5yb=JnwY_rMYwTOHjU3izoA8wxfRVgfAGK9zWh=7NZ7H23Q@mail.gmail.com>

On Tue, 2 Apr 2019 19:06:37 +0800
Zhuohao Lee <zhuohao@chromium.org> wrote:

> On Tue, Apr 2, 2019 at 4:26 PM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> >
> >
> >
> > On 02/04/19 1:26 PM, Boris Brezillon wrote:  
> > > On Tue, 2 Apr 2019 15:39:54 +0800
> > > Zhuohao Lee <zhuohao@chromium.org> wrote:
> > >  
> > >> Thanks Boris for the comment. Please take a look the reply at below.
> > >>
> > >> On Mon, Apr 1, 2019 at 5:27 PM Boris Brezillon
> > >> <boris.brezillon@collabora.com> wrote:  
> > >>>
> > >>> On Thu, 28 Mar 2019 12:59:10 +0800
> > >>> Zhuohao Lee <zhuohao@chromium.org> wrote:
> > >>>  
> > >>>> Currently, we don't have sysfs nodes for querying the underlying flash
> > >>>> name and flash id. This information is important especially when we
> > >>>> want to know the flash detail of the defective system. In order to
> > >>>> support the query, we add two pointers (*flashname, *id) into the
> > >>>> mtd_info structure and create two sysfs nodes (flashname, id). This
> > >>>> patch is modified based on the SPI-NOR flash system as we only have
> > >>>> that system now. But the idea should be applied to the other flash
> > >>>> driver like NAND flash.
> > >>>>
> > >>>> The output of new sysfs nodes on my device are:
> > >>>> cat /sys/devices/platform/soc/11010000.spi/spi_master/spi1/spi1.0/mtd/mtd0/flashname
> > >>>> w25q64dw
> > >>>> cat /sys/devices/platform/soc/11010000.spi/spi_master/spi1/spi1.0/mtd/mtd0/id
> > >>>> ef6017  
> > >>>
> > >>> I'm not sure I like the idea of exposing this kind of info through
> > >>> sysfs as it then makes part of the ABI. Did you consider exposing that
> > >>> through debugfs?  
> > >>
> > >> Yes, i did consider the debugfs. I think the debugfs is depended on
> > >> CONFIG_DEBUG_FS.
> > >> If removing that config, the partname and partid will be lost. So, i
> > >> proposed to use
> > >> sysfs.  
> > >
> > > Then just enable debugfs if you need this information :P.  
> My original intention is adding the new sysfs nodes (i.e partname and
> partid) into the common place like mtdcore.c
> so that the userspace program can just read the common sysfs nodes.
> So far, what i can contribute is for the spi-nor but if the other
> flash drivers, like nand-flash, can also support
> the partname and partid query, then, we can have common sysfs nodes to
> query the underlying device info.
> Compare to the debugfs, i think different drivers may have different
> name for the partname and partid.

We've recently unified how MTD related stuff are exposed through
debugfs and you can now have generic MTD fields exposed there.

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