| Message ID | 20221021064453.3341050-1-gregkh@linuxfoundation.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | USB: gadget: dummy_hcd: switch char * to u8 * | expand |
On Sun, Oct 23, 2022 at 05:53:19PM +0200, Greg Kroah-Hartman wrote: > On Fri, Oct 21, 2022 at 10:30:37AM -0700, Linus Torvalds wrote: > > On Thu, Oct 20, 2022 at 11:44 PM Greg Kroah-Hartman > > <gregkh@linuxfoundation.org> wrote: > > > > > > The function handle_control_request() casts the urb buffer to a char *, > > > and then treats it like a unsigned char buffer when assigning data to > > > it. On some architectures, "char" is really signed, so let's just > > > properly set this pointer to a u8 to take away any potential problems as > > > that's what is really wanted here. > > > > I think you might as well also remove the cast that was always a bit odd: > > > > buf[0] = (u8)dum->devstatus; > > > > although maybe it's intentional ("look, ma, I'm truncating this > > value") because 'devstatus' is a 'u16' type? > > (adding Alan as he's the owner of this file now) > > Yes, devstatus is a u16 as that's what the USB spec says it should be, > but so far only 7 of the lower bits have been used. I guess to do this > properly we should also copy the upper 8 bits in to buf[1], eventhough > in reality it's only ever going to be 0x00 for now. Along these lines, do we really not have a predefined macro/inline function that does: (value >> 8) to give you the "high byte" of a 16bit value? I keep seeing people write their own macros for this in staging drivers, but I just attributed that to them not using the correct in-kernel macro, but I can't seem to find anything at the moment to do this (same with "give me just the lower 8 bits of a 16bit value"). Am I just blind? It's not like it's complex or tricky stuff, I just thought we had something in bits.h or bitops.h or the like. Oh well... thanks, greg k-h
On Sun, Oct 23, 2022 at 9:04 AM Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > > Along these lines, do we really not have a predefined macro/inline > function that does: > (value >> 8) > to give you the "high byte" of a 16bit value? No macros like that. And honestly, why would you want a macro that is more complicated than the operation itself? But it sounds like what you actually want is just put_unaligned_le16(dum->devstatus, buf); which does both bytes correctly (and turns into a plain 16-bit store on sane architectures).. Linus
diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c index 899ac9f9c279..774781968e55 100644 --- a/drivers/usb/gadget/udc/dummy_hcd.c +++ b/drivers/usb/gadget/udc/dummy_hcd.c @@ -1740,13 +1740,13 @@ static int handle_control_request(struct dummy_hcd *dum_hcd, struct urb *urb, if (setup->bRequestType == Dev_InRequest || setup->bRequestType == Intf_InRequest || setup->bRequestType == Ep_InRequest) { - char *buf; + u8 *buf; /* * device: remote wakeup, selfpowered * interface: nothing * endpoint: halt */ - buf = (char *)urb->transfer_buffer; + buf = urb->transfer_buffer; if (urb->transfer_buffer_length > 0) { if (setup->bRequestType == Ep_InRequest) { ep2 = find_endpoint(dum, w_index);
The function handle_control_request() casts the urb buffer to a char *, and then treats it like a unsigned char buffer when assigning data to it. On some architectures, "char" is really signed, so let's just properly set this pointer to a u8 to take away any potential problems as that's what is really wanted here. Cc: Felipe Balbi <balbi@kernel.org> Cc: Jakob Koschel <jakobkoschel@gmail.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Ira Weiny <ira.weiny@intel.com> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/usb/gadget/udc/dummy_hcd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)