| Message ID | 20180907142247.2931-1-thierry.reding@gmail.com |
|---|---|
| State | Rejected, archived |
| Headers | show |
| Series | of: Split up name & type in modalias generation | expand |
On 09/07/18 07:22, Thierry Reding wrote: > From: Thierry Reding <treding@nvidia.com> > > The kernel's vsnprintf() implementation discards all alpha-numeric > characters following a %p conversion specifier. This is done in order to > generically skip any of the various modifiers that the kernel supports. > Unfortunately, the OF modalias is generated with a format string that > violates the assumption made by vsnprintf(): > > of:N%pOFnT%s > > While processing the above format string, vsnprintf() will eat the 'T' > character, assuming that it belongs to the preceeding %p specifier. This > results in a modalias with an incompatible format, which in turn causes > the automatic loading of drivers based on modalias to no longer work. > > To fix this, split up the generation of the name & type fields into two > separate snprintf() calls to avoid confusing the parser. > > Fixes: 73813f8483b1 ("of: Convert to using %pOFn instead of device_node.name") > Signed-off-by: Thierry Reding <treding@nvidia.com> > --- > Note that a more elegant fix would be to make the %p format specifier > parser report back the exact number of characters consumed. I briefly > tried to implement it, but quickly ran into numerous special cases > that make this solution rather involved. > > I can spend some more time to improve this in general if that's what we > ultimately want, but I think this patch is a better short-term fix to > workaround the issue. > --- > drivers/of/device.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/of/device.c b/drivers/of/device.c > index daa075d87317..dabef9fc8538 100644 > --- a/drivers/of/device.c > +++ b/drivers/of/device.c > @@ -218,14 +218,20 @@ static ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len > if ((!dev) || (!dev->of_node)) > return -ENODEV; > > - /* Name & Type */ > - csize = snprintf(str, len, "of:N%pOFnT%s", dev->of_node, > - dev->of_node->type); > + /* Name */ > + csize = snprintf(str, len, "of:N%pOFn", dev->of_node); > tsize = csize; > len -= csize; > if (str) > str += csize; > > + /* Type */ > + csize = snprintf(str, len, "T%s", dev->of_node->type); > + tsize += csize; > + len -= csize; > + if (str) > + str += csize; > + > of_property_for_each_string(dev->of_node, "compatible", p, compat) { > csize = strlen(compat) + 1; > tsize += csize; > Reviewed-by: Frank Rowand <frank.rowand@sony.com>
On Fri, Sep 7, 2018 at 9:22 AM Thierry Reding <thierry.reding@gmail.com> wrote: > > From: Thierry Reding <treding@nvidia.com> > > The kernel's vsnprintf() implementation discards all alpha-numeric > characters following a %p conversion specifier. This is done in order to > generically skip any of the various modifiers that the kernel supports. > Unfortunately, the OF modalias is generated with a format string that > violates the assumption made by vsnprintf(): > > of:N%pOFnT%s > > While processing the above format string, vsnprintf() will eat the 'T' > character, assuming that it belongs to the preceeding %p specifier. This > results in a modalias with an incompatible format, which in turn causes > the automatic loading of drivers based on modalias to no longer work. > > To fix this, split up the generation of the name & type fields into two > separate snprintf() calls to avoid confusing the parser. > > Fixes: 73813f8483b1 ("of: Convert to using %pOFn instead of device_node.name") > Signed-off-by: Thierry Reding <treding@nvidia.com> > --- > Note that a more elegant fix would be to make the %p format specifier > parser report back the exact number of characters consumed. I briefly > tried to implement it, but quickly ran into numerous special cases > that make this solution rather involved. > > I can spend some more time to improve this in general if that's what we > ultimately want, but I think this patch is a better short-term fix to > workaround the issue. See my reply on the original patch. I've updated the patch in my dt/next branch with the fix to use %c. Rob
On 09/07/18 11:49, Rob Herring wrote: > On Fri, Sep 7, 2018 at 9:22 AM Thierry Reding <thierry.reding@gmail.com> wrote: >> >> From: Thierry Reding <treding@nvidia.com> >> >> The kernel's vsnprintf() implementation discards all alpha-numeric >> characters following a %p conversion specifier. This is done in order to >> generically skip any of the various modifiers that the kernel supports. >> Unfortunately, the OF modalias is generated with a format string that >> violates the assumption made by vsnprintf(): >> >> of:N%pOFnT%s >> >> While processing the above format string, vsnprintf() will eat the 'T' >> character, assuming that it belongs to the preceeding %p specifier. This >> results in a modalias with an incompatible format, which in turn causes >> the automatic loading of drivers based on modalias to no longer work. >> >> To fix this, split up the generation of the name & type fields into two >> separate snprintf() calls to avoid confusing the parser. >> >> Fixes: 73813f8483b1 ("of: Convert to using %pOFn instead of device_node.name") >> Signed-off-by: Thierry Reding <treding@nvidia.com> >> --- >> Note that a more elegant fix would be to make the %p format specifier >> parser report back the exact number of characters consumed. I briefly >> tried to implement it, but quickly ran into numerous special cases >> that make this solution rather involved. >> >> I can spend some more time to improve this in general if that's what we >> ultimately want, but I think this patch is a better short-term fix to >> workaround the issue. > > See my reply on the original patch. I've updated the patch in my > dt/next branch with the fix to use %c. > > Rob > Agreed, your updated patch is more compact and looks cleaner. -Frank
On Fri, Sep 07, 2018 at 12:56:09PM -0700, Frank Rowand wrote: > On 09/07/18 11:49, Rob Herring wrote: > > On Fri, Sep 7, 2018 at 9:22 AM Thierry Reding <thierry.reding@gmail.com> wrote: > >> > >> From: Thierry Reding <treding@nvidia.com> > >> > >> The kernel's vsnprintf() implementation discards all alpha-numeric > >> characters following a %p conversion specifier. This is done in order to > >> generically skip any of the various modifiers that the kernel supports. > >> Unfortunately, the OF modalias is generated with a format string that > >> violates the assumption made by vsnprintf(): > >> > >> of:N%pOFnT%s > >> > >> While processing the above format string, vsnprintf() will eat the 'T' > >> character, assuming that it belongs to the preceeding %p specifier. This > >> results in a modalias with an incompatible format, which in turn causes > >> the automatic loading of drivers based on modalias to no longer work. > >> > >> To fix this, split up the generation of the name & type fields into two > >> separate snprintf() calls to avoid confusing the parser. > >> > >> Fixes: 73813f8483b1 ("of: Convert to using %pOFn instead of device_node.name") > >> Signed-off-by: Thierry Reding <treding@nvidia.com> > >> --- > >> Note that a more elegant fix would be to make the %p format specifier > >> parser report back the exact number of characters consumed. I briefly > >> tried to implement it, but quickly ran into numerous special cases > >> that make this solution rather involved. > >> > >> I can spend some more time to improve this in general if that's what we > >> ultimately want, but I think this patch is a better short-term fix to > >> workaround the issue. > > > > See my reply on the original patch. I've updated the patch in my > > dt/next branch with the fix to use %c. > > > > Rob > > > > Agreed, your updated patch is more compact and looks cleaner. Not sure about "cleaner", but yeah, that works as well. Thierry
diff --git a/drivers/of/device.c b/drivers/of/device.c index daa075d87317..dabef9fc8538 100644 --- a/drivers/of/device.c +++ b/drivers/of/device.c @@ -218,14 +218,20 @@ static ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len if ((!dev) || (!dev->of_node)) return -ENODEV; - /* Name & Type */ - csize = snprintf(str, len, "of:N%pOFnT%s", dev->of_node, - dev->of_node->type); + /* Name */ + csize = snprintf(str, len, "of:N%pOFn", dev->of_node); tsize = csize; len -= csize; if (str) str += csize; + /* Type */ + csize = snprintf(str, len, "T%s", dev->of_node->type); + tsize += csize; + len -= csize; + if (str) + str += csize; + of_property_for_each_string(dev->of_node, "compatible", p, compat) { csize = strlen(compat) + 1; tsize += csize;