Messages in this thread | | | Date | Tue, 02 Mar 2021 17:19:55 +0100 | From | Michael Walle <> | Subject | Re: [RFC PATCH] mtd: add OTP (one-time-programmable) erase ioctl |
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Am 2021-03-02 16:30, schrieb Vignesh Raghavendra: > Hi, > > On 3/2/21 4:39 PM, Michael Walle wrote: >> This may sound like a contradiction but some SPI-NOR flashes really >> support erasing their OTP region until it is finally locked. Having >> the >> possibility to erase an OTP region might come in handy during >> development. >> >> The ioctl argument follows the OTPLOCK style. >> >> Signed-off-by: Michael Walle <michael@walle.cc> >> --- >> OTP support for SPI-NOR flashes may be merged soon: >> https://lore.kernel.org/linux-mtd/20210216162807.13509-1-michael@walle.cc/ >> >> Tudor suggested to add support for the OTP erase operation most >> SPI-NOR >> flashes have: >> https://lore.kernel.org/linux-mtd/d4f74b1b-fa1b-97ec-858c-d807fe1f9e57@microchip.com/ >> >> Therefore, this is an RFC to get some feedback on the MTD side, once >> this >> is finished, I can post a patch for mtd-utils. Then we'll have a >> foundation >> to add the support to SPI-NOR. >> >> drivers/mtd/mtdchar.c | 7 ++++++- >> drivers/mtd/mtdcore.c | 12 ++++++++++++ >> include/linux/mtd/mtd.h | 3 +++ >> include/uapi/mtd/mtd-abi.h | 2 ++ >> 4 files changed, 23 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c >> index 323035d4f2d0..da423dd031ae 100644 >> --- a/drivers/mtd/mtdchar.c >> +++ b/drivers/mtd/mtdchar.c >> @@ -661,6 +661,7 @@ static int mtdchar_ioctl(struct file *file, u_int >> cmd, u_long arg) >> case OTPGETREGIONCOUNT: >> case OTPGETREGIONINFO: >> case OTPLOCK: >> + case OTPERASE: > > This is not a Safe IOCTL. We are destroying OTP data. Need to check for > write permission before allowing the ioctl right?
Ah yes, of course. But this makes me wonder why OTPLOCK is considered a safe command. As well as MEMLOCK and MEMUNLOCK. And MEMSETBADBLOCK. Shouldn't these also require write permissions?
>> case ECCGETLAYOUT: >> case ECCGETSTATS: >> case MTDFILEMODE: >> @@ -938,6 +939,7 @@ static int mtdchar_ioctl(struct file *file, u_int >> cmd, u_long arg) >> } >> >> case OTPLOCK: >> + case OTPERASE: >> { >> struct otp_info oinfo; >> >> @@ -945,7 +947,10 @@ static int mtdchar_ioctl(struct file *file, u_int >> cmd, u_long arg) >> return -EINVAL; >> if (copy_from_user(&oinfo, argp, sizeof(oinfo))) >> return -EFAULT; >> - ret = mtd_lock_user_prot_reg(mtd, oinfo.start, oinfo.length); >> + if (cmd == OTPLOCK) >> + ret = mtd_lock_user_prot_reg(mtd, oinfo.start, oinfo.length); >> + else >> + ret = mtd_erase_user_prot_reg(mtd, oinfo.start, oinfo.length); >> break; >> } >> >> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c >> index 2d6423d89a17..d844d718ef77 100644 >> --- a/drivers/mtd/mtdcore.c >> +++ b/drivers/mtd/mtdcore.c >> @@ -1918,6 +1918,18 @@ int mtd_lock_user_prot_reg(struct mtd_info >> *mtd, loff_t from, size_t len) >> } >> EXPORT_SYMBOL_GPL(mtd_lock_user_prot_reg); >> >> +int mtd_erase_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t >> len) >> +{ >> + struct mtd_info *master = mtd_get_master(mtd); >> + >> + if (!master->_erase_user_prot_reg) >> + return -EOPNOTSUPP; >> + if (!len) >> + return 0; >> + return master->_erase_user_prot_reg(master, from, len); >> +} >> +EXPORT_SYMBOL_GPL(mtd_erase_user_prot_reg); >> + >> /* Chip-supported device locking */ >> int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len) >> { >> diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h >> index 157357ec1441..734ad7a8c353 100644 >> --- a/include/linux/mtd/mtd.h >> +++ b/include/linux/mtd/mtd.h >> @@ -336,6 +336,8 @@ struct mtd_info { >> size_t len, size_t *retlen, u_char *buf); >> int (*_lock_user_prot_reg) (struct mtd_info *mtd, loff_t from, >> size_t len); >> + int (*_erase_user_prot_reg) (struct mtd_info *mtd, loff_t from, >> + size_t len); >> int (*_writev) (struct mtd_info *mtd, const struct kvec *vecs, >> unsigned long count, loff_t to, size_t *retlen); >> void (*_sync) (struct mtd_info *mtd); >> @@ -517,6 +519,7 @@ int mtd_read_user_prot_reg(struct mtd_info *mtd, >> loff_t from, size_t len, >> int mtd_write_user_prot_reg(struct mtd_info *mtd, loff_t to, size_t >> len, >> size_t *retlen, u_char *buf); >> int mtd_lock_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t >> len); >> +int mtd_erase_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t >> len); >> >> int mtd_writev(struct mtd_info *mtd, const struct kvec *vecs, >> unsigned long count, loff_t to, size_t *retlen); >> diff --git a/include/uapi/mtd/mtd-abi.h b/include/uapi/mtd/mtd-abi.h >> index 65b9db936557..242015f60d10 100644 >> --- a/include/uapi/mtd/mtd-abi.h >> +++ b/include/uapi/mtd/mtd-abi.h >> @@ -205,6 +205,8 @@ struct otp_info { >> * without OOB, e.g., NOR flash. >> */ >> #define MEMWRITE _IOWR('M', 24, struct mtd_write_req) >> +/* Erase a given range of user data (must be in mode >> %MTD_FILE_MODE_OTP_USER) */ >> +#define OTPERASE _IOR('M', 25, struct otp_info) >> > > Hmm, shouldn't this be: > > #define OTPERASE _IOW('M', 25, struct otp_info) > > Userspace is writing struct otp_info to the driver. OTPLOCK should > probably be _IOW() as well.
You're right.
NB. most OTP commands have a wrong direction flag.
>> /* >> * Obsolete legacy interface. Keep it in order not to break userspace >>
-michael
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