linux-kernel - Re: [Uclinux-dist-devel] [PATCH 1/2] mtd: m25p80: Reworkprobing/JEDEC code

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Message-ID: <AANLkTiknH95loHJsQNxvCCyQbriCFWqM5LHl3wKzmdWX@mail.gmail.com>
Date:	Mon, 21 Jun 2010 15:22:48 +0800
From:	Barry Song <21cnbao@...il.com>
To:	Anton Vorontsov <cbouatmailru@...il.com>
Cc:	"Song, Barry" <Barry.Song@...log.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Artem Bityutskiy <dedekind1@...il.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	linux-mtd@...ts.infradead.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Uclinux-dist-devel] [PATCH 1/2] mtd: m25p80: Reworkprobing/JEDEC 
	code

On Mon, Jun 21, 2010 at 3:15 PM, Anton Vorontsov <cbouatmailru@...il.com> wrote:
> On Mon, Jun 21, 2010 at 11:27:31AM +0800, Barry Song wrote:
> [...]
>> > How about we add a non_jedec flag in platform_data, if the flag is 1, we
>> > let the detection pass even though the ID is 0? Otherwise, we need a
>> > valid ID?
>> Here i mean:
>
> This will break at least OF-enabled platforms (e.g. PowerPC),
> they assume that the driver will success for non-JEDEC flashes.
> OF platforms don't pass platform data, and even if they did,
> device tree doesn't specify if the flash is JEDEC or non-JEDEC.
>
> Which is why I think that, by default, the driver should
> successfully register the flash even if JEDEC probe fails. So,
> instead of checking for "!non_jedec", I would recommend
> "force_jedec" check.

Mike Frysinger suggested to use non_jedec since most devices are
standard jedec devices. Only if non_jedec=1, we let the detection pass
if ID is 0.

>
>> Index: drivers/mtd/devices/m25p80.c
>> ===================================================================
>> --- drivers/mtd/devices/m25p80.c      (revision 8927)
>> +++ drivers/mtd/devices/m25p80.c      (revision 8929)
>> @@ -795,8 +795,13 @@
>>
>>               jid = jedec_probe(spi);
>>               if (!jid) {
>> -                     dev_info(&spi->dev, "non-JEDEC variant of %s\n",
>> -                              id->name);
>> +                     if (!data->non_jedec) {
>> +                             dev_err(&spi->dev, "fail to detect%s\n",
>> +                                             id->name);
>> +                             return -ENODEV;
>> +                     } else
>> +                             dev_info(&spi->dev, "non-JEDEC variant of %s\n",
>> +                                             id->name);
>>               } else if (jid != id) {
>
> --
> Anton Vorontsov
> email: cbouatmailru@...il.com
> irc://irc.freenode.net/bd2
>