Message ID | 1345925210-7500-1-git-send-email-shijie8@gmail.com |
---|---|
State | New, archived |
Headers | show |
Hi Huang, Artem, On Sat, 25 Aug 2012 16:06:50 -0400 Huang Shijie <shijie8@gmail.com> wrote: > diff --git a/drivers/mtd/cmdlinepart.c b/drivers/mtd/cmdlinepart.c > index fc960a3..216d751 100644 > --- a/drivers/mtd/cmdlinepart.c > +++ b/drivers/mtd/cmdlinepart.c > @@ -322,13 +322,16 @@ static int parse_cmdline_partitions(struct mtd_info *master, > struct cmdline_mtd_partition *part; > const char *mtd_id = master->name; > > + if (!mtd_id) > + return 0; > + > /* parse command line */ > if (!cmdline_parsed) > mtdpart_setup_real(cmdline); > > for(part = partitions; part; part = part->next) > { > - if ((!mtd_id) || (!strcmp(part->mtd_id, mtd_id))) > + if (!strcmp(part->mtd_id, mtd_id)) > { > for(i = 0, offset = 0; i < part->num_parts; i++) > { This changes the behavior of cmdling parsing, which might affect users expecting the old behavior. According to the remark above 'parse_cmdline_partitions': * It returns partitions for the requested mtd device, or * the first one in the chain if a NULL mtd_id is passed in. I think the purpose of a NULL 'mtd_id' was to support simple systems where there's a single driver and a single chip. The driver could be dumb, not specifying its 'mtd_info->name' (thus, a NULL mtd_id is passed). In this case, since the system is simply configured (one driver, one chip), 'parse_cmdline_partitions' simply disregards the "mtd-id" name specified in the cmdline string, allowing the user to present some arbitrary string there. I quite remember seeing this pattern somewhere in the past, I don't know if it's still used, though. Obviously if you have many drivers (and many chips) in a system, that won't work; the drivers must initialize 'mtd_info->name' and the user should present a cmdline that has explicit 'mtd-id's. So question is, would we like to prohibit NULL mtd-id? If so, we must make sure all drivers are properly assigning their 'mtd_info->name', and all users correctly specifying 'mtd-id' in their "mtdparts" cmdline strings. Regards, Shmulik
On Sat, Aug 25, 2012 at 5:31 AM, Shmulik Ladkani <shmulik.ladkani@gmail.com> wrote: > Hi Huang, Artem, > > On Sat, 25 Aug 2012 16:06:50 -0400 Huang Shijie <shijie8@gmail.com> wrote: >> diff --git a/drivers/mtd/cmdlinepart.c b/drivers/mtd/cmdlinepart.c >> index fc960a3..216d751 100644 >> --- a/drivers/mtd/cmdlinepart.c >> +++ b/drivers/mtd/cmdlinepart.c >> @@ -322,13 +322,16 @@ static int parse_cmdline_partitions(struct mtd_info *master, >> struct cmdline_mtd_partition *part; >> const char *mtd_id = master->name; >> >> + if (!mtd_id) >> + return 0; >> + >> /* parse command line */ >> if (!cmdline_parsed) >> mtdpart_setup_real(cmdline); >> >> for(part = partitions; part; part = part->next) >> { >> - if ((!mtd_id) || (!strcmp(part->mtd_id, mtd_id))) >> + if (!strcmp(part->mtd_id, mtd_id)) >> { >> for(i = 0, offset = 0; i < part->num_parts; i++) >> { > > This changes the behavior of cmdling parsing, which might affect users > expecting the old behavior. > > According to the remark above 'parse_cmdline_partitions': > > * It returns partitions for the requested mtd device, or > * the first one in the chain if a NULL mtd_id is passed in. > > I think the purpose of a NULL 'mtd_id' was to support simple systems > where there's a single driver and a single chip. > The driver could be dumb, not specifying its 'mtd_info->name' > (thus, a NULL mtd_id is passed). > > In this case, since the system is simply configured (one driver, one > chip), 'parse_cmdline_partitions' simply disregards the "mtd-id" name > specified in the cmdline string, allowing the user to present some > arbitrary string there. > > I quite remember seeing this pattern somewhere in the past, I don't know > if it's still used, though. > thanks for the detail explanation. > Obviously if you have many drivers (and many chips) in a system, that > won't work; the drivers must initialize 'mtd_info->name' and the user > should present a cmdline that has explicit 'mtd-id's. > > So question is, would we like to prohibit NULL mtd-id? I prefer to prohibit the NULL mtd-id. The code looks strange enough. > > If so, we must make sure all drivers are properly assigning their > 'mtd_info->name', and all users correctly specifying 'mtd-id' in their > "mtdparts" cmdline strings. yes. I agree that all the driver should set the mtd_info->name properly. Best Regards Huang Shijie > > Regards, > Shmulik
On Sat, 2012-08-25 at 12:31 +0300, Shmulik Ladkani wrote: > Hi Huang, Artem, > > On Sat, 25 Aug 2012 16:06:50 -0400 Huang Shijie <shijie8@gmail.com> wrote: > > diff --git a/drivers/mtd/cmdlinepart.c b/drivers/mtd/cmdlinepart.c > > index fc960a3..216d751 100644 > > --- a/drivers/mtd/cmdlinepart.c > > +++ b/drivers/mtd/cmdlinepart.c > > @@ -322,13 +322,16 @@ static int parse_cmdline_partitions(struct mtd_info *master, > > struct cmdline_mtd_partition *part; > > const char *mtd_id = master->name; > > > > + if (!mtd_id) > > + return 0; > > + > > /* parse command line */ > > if (!cmdline_parsed) > > mtdpart_setup_real(cmdline); > > > > for(part = partitions; part; part = part->next) > > { > > - if ((!mtd_id) || (!strcmp(part->mtd_id, mtd_id))) > > + if (!strcmp(part->mtd_id, mtd_id)) > > { > > for(i = 0, offset = 0; i < part->num_parts; i++) > > { > > This changes the behavior of cmdling parsing, which might affect users > expecting the old behavior. Yes, you are right, we should not change the mtd_id hack unless we have checked all the users.
diff --git a/drivers/mtd/cmdlinepart.c b/drivers/mtd/cmdlinepart.c index fc960a3..216d751 100644 --- a/drivers/mtd/cmdlinepart.c +++ b/drivers/mtd/cmdlinepart.c @@ -322,13 +322,16 @@ static int parse_cmdline_partitions(struct mtd_info *master, struct cmdline_mtd_partition *part; const char *mtd_id = master->name; + if (!mtd_id) + return 0; + /* parse command line */ if (!cmdline_parsed) mtdpart_setup_real(cmdline); for(part = partitions; part; part = part->next) { - if ((!mtd_id) || (!strcmp(part->mtd_id, mtd_id))) + if (!strcmp(part->mtd_id, mtd_id)) { for(i = 0, offset = 0; i < part->num_parts; i++) {
The `mtd_id` is set by the name of a mtd device driver. As a nand controller driver, even we do not set the @name of the mtd_info{}, the nand_get_flash_type() will set it with the nand type's name. So the `mtd_id` can never be NULL in this case. But as a nor controller driver which may does not call the nand_get_flash_type(), there is a risk that the `mtd_id` becames NULL. If the `mtd_id` is NULL, the check condition will be true. If we accidentally set some partitions in the kernel command line, just like: #gpmi-nand:20m(boot),20m(kernel),1g(rootfs),-(user) The cmdlinepart may parses out several mtd partitions right now. This is obviously wrong. We even do not enable the gpmi-nand in this case. The patch comes from Artem's suggestion code which is better then mine. Signed-off-by: Huang Shijie <shijie8@gmail.com> --- drivers/mtd/cmdlinepart.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-)