Messages in this thread | | | Subject | Re: [PATCH] mtd: core: handle flashes without OTP gracefully | From | Guenter Roeck <> | Date | Tue, 6 Jul 2021 11:22:37 -0700 |
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On 7/6/21 9:29 AM, Miquel Raynal wrote: > 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. >
The check in mtd_otp_nvmem_add() does not affect userspace.
Guenter
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