On Thu, Feb 28, 2019 at 4:28 AM Louis Taylor <louis@xxxxxxxxxx> wrote: > > When compiling with -Wformat, clang warns: > > ./include/linux/usb/wusb.h:245:5: warning: format specifies type > 'unsigned short' but the argument has type 'u8' (aka 'unsigned char') We should probably update Documentation/core-api/printk-formats.rst to list [u|s][8|16] printk formats so that I don't have to go read lib/vsprintf.c#format_decode(). (TODO in a separate patch) > [-Wformat] > ckhdid->data[0], ckhdid->data[1], > ^~~~~~~~~~~~~~~ > > ckhdid->data is unconditionally defined as `u8 data[16]`, so this patch > updates the format characters to the correct one for unsigned char types. > > Link: https://github.com/ClangBuiltLinux/linux/issues/378 > Signed-off-by: Louis Taylor <louis@xxxxxxxxxx> > --- > include/linux/usb/wusb.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/usb/wusb.h b/include/linux/usb/wusb.h > index 9e4a3213f2c2..625366d3499e 100644 > --- a/include/linux/usb/wusb.h > +++ b/include/linux/usb/wusb.h > @@ -240,8 +240,8 @@ static inline size_t ckhdid_printf(char *pr_ckhdid, size_t size, > const struct wusb_ckhdid *ckhdid) > { > return scnprintf(pr_ckhdid, size, > - "%02hx %02hx %02hx %02hx %02hx %02hx %02hx %02hx " > - "%02hx %02hx %02hx %02hx %02hx %02hx %02hx %02hx", > + "%02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx " > + "%02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx", Looks like lib/vsprintf.c#format_decode() accepts either %hh or %H for lone unsigned bytes, IIUC. Thanks for the patch and for following up on the feedback. Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> I wonder if __attribute__((packed)) is needed on the definition of `struct wusb_ckhdid`? hmm... via Stephen: https://godbolt.org/z/vs5JNo Looks like alignof(struct wusb_ckhdid) is 1. And struct wusb_ckhdid was introduced as is in commit c7f736484f8e ("wusb: add the Wireless USB include files.") so it's not like it ever had additional members that would disturb the alignment. `__aligned(__alignof__(u8))` might be clearer than `__attribute__((packed))`, but even then, I don't think anything is necessary since the alignof should always be 1? > ckhdid->data[0], ckhdid->data[1], > ckhdid->data[2], ckhdid->data[3], > ckhdid->data[4], ckhdid->data[5], > -- > 2.20.1 > -- Thanks, ~Nick Desaulniers
