Messages in this thread | | | Date | Tue, 6 Jul 2021 18:29:08 +0200 | From | Miquel Raynal <> | Subject | Re: [PATCH] mtd: core: handle flashes without OTP gracefully |
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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
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