From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Tudor.Ambarus@microchip.com, michael@walle.cc,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
richard@nod.at, vigneshr@ti.com
Subject: Re: [PATCH] mtd: core: handle flashes without OTP gracefully
Date: Tue, 6 Jul 2021 18:29:08 +0200 [thread overview]
Message-ID: <20210706182908.3cf82669@xps13> (raw)
In-Reply-To: <2716acf0-fcf1-d2ef-83be-152d0300d687@roeck-us.net>
Hi Guenter,
Guenter Roeck <linux@roeck-us.net> wrote on Sat, 3 Jul 2021 10:26:06
-0700:
> On 7/3/21 9:42 AM, Tudor.Ambarus@microchip.com wrote:
> > On 7/3/21 7:08 PM, Michael Walle wrote:
> >> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >>
> >> Am 3. Juli 2021 11:56:14 MESZ schrieb Tudor.Ambarus@microchip.com:
> >>> On 7/2/21 12:38 PM, Michael Walle wrote:
> >>>> EXTERNAL EMAIL: Do not click links or open attachments unless you
> >>> know the content is safe
> >>>>
> >>>> There are flash drivers which registers the OTP callbacks although
> >>> the
> >>>> flash doesn't support OTP regions and return -ENODATA for these
> >>>> callbacks if there is no OTP. If this happens, the probe of the whole
> >>>
> >>> why do they register the OTP callback if they don't support OTP?
> >>
> >> I don't know. But I certainly won't touch that code :p
> >
> > why? :D
> >
> >>
> >>
> >>>> flash will fail. Fix it by handling the ENODATA return code and skip
> >>>> the OTP region nvmem setup.
> >>>>
> >>>> Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support")
> >>>> Reported-by: Guenter Roeck <linux@roeck-us.net>
> >>>> Signed-off-by: Michael Walle <michael@walle.cc>
> >>>> ---
> >>>> drivers/mtd/mtdcore.c | 10 ++++++++--
> >>>> 1 file changed, 8 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> >>>> index b5ccd3037788..6881d1423dd6 100644
> >>>> --- a/drivers/mtd/mtdcore.c
> >>>> +++ b/drivers/mtd/mtdcore.c
> >>>> @@ -880,7 +880,10 @@ static int mtd_otp_nvmem_add(struct mtd_info
> >>> *mtd)
> >>>>
> >>>> if (mtd->_get_user_prot_info && mtd->_read_user_prot_reg) {
> >>>> size = mtd_otp_size(mtd, true);
> >>>> - if (size < 0)
> >>>> + /* ENODATA means there is no OTP region */
> >>>> + if (size == -ENODATA)
> >>>
> >>> If no OTP data, maybe it's more appropriate for the clients to just
> >>> return a retlen of 0.
> >>
> >> you mean already checking ENODATA in mtd_otp_size() and return 0. That would also make the hunk below unnecessary. I'll change it.
> >
> > I've thought about:
> >
> > diff --git a/drivers/mtd/chips/cfi_cmdset_0001.c b/drivers/mtd/chips/cfi_cmdset_0001.c
> > index 54f92d09d9cf..9419b33d7238 100644
> > --- a/drivers/mtd/chips/cfi_cmdset_0001.c
> > +++ b/drivers/mtd/chips/cfi_cmdset_0001.c
> > @@ -2314,7 +2314,7 @@ static int cfi_intelext_otp_walk(struct mtd_info *mtd, loff_t from, size_t len,
> > > /* Check that we actually have some OTP registers */
> > if (!extp || !(extp->FeatureSupport & 64) || !extp->NumProtectionFields)
> > - return -ENODATA;
> > + return 0;
> >
>
> There are various places where this is called, including code returning information
> to userspace. That means you'd be changing the ABI to userspace which would now suddenly
> return 0 instead of -ENODATA.
Yeah let's avoid this if possible, even though I liked Tudor's approach.
Would Michael proposal of checking it in mtd_otp_size() still affect
userspace? If not, having a single check over the -ENODATA return code
seems attractive.
Thanks,
Miquèl
next prev parent reply other threads:[~2021-07-06 16:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-02 9:38 [PATCH] mtd: core: handle flashes without OTP gracefully Michael Walle
2021-07-02 13:49 ` Guenter Roeck
2021-07-02 13:53 ` Michael Walle
2021-07-03 9:56 ` Tudor.Ambarus
2021-07-03 16:08 ` Michael Walle
2021-07-03 16:42 ` Tudor.Ambarus
2021-07-03 17:26 ` Guenter Roeck
2021-07-06 16:29 ` Miquel Raynal [this message]
2021-07-06 18:22 ` Guenter Roeck
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