On 09/07/18 07:22, Thierry Reding wrote: > From: Thierry Reding <[email protected]> > > 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 <[email protected]> > --- > 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 <[email protected]>
