Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 於 2022年1月6日 週四 下午10:35寫道： > > On Wed, Jan 05, 2022 at 12:04:39PM +0800, Wei Ming Chen wrote: > > There will be 2 leading bytes indicating the total length of > > the PNP string, so I think we should add value by 2, otherwise > > the PNP string copied to user will not contain the last 2 bytes > > > > Signed-off-by: Wei Ming Chen <jj251510319013@xxxxxxxxx> > > --- > > drivers/usb/gadget/function/f_printer.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c > > index abec5c58f525..3fb00fd0b5ee 100644 > > --- a/drivers/usb/gadget/function/f_printer.c > > +++ b/drivers/usb/gadget/function/f_printer.c > > @@ -1005,9 +1005,11 @@ static int printer_func_setup(struct usb_function *f, > > break; > > } > > value = strlen(dev->pnp_string); > > + memcpy(buf + 2, dev->pnp_string, value); > > + > > + value += 2; > > buf[0] = (value >> 8) & 0xFF; > > buf[1] = value & 0xFF; > > - memcpy(buf + 2, dev->pnp_string, value); > > DBG(dev, "1284 PNP String: %x %s\n", value, > > dev->pnp_string); > > break; > > -- > > 2.25.1 > > > > Are you sure this is correct? > > How is this related to this recent thread: > https://lore.kernel.org/all/CAKjGFBUdjXcZoVV4jdrgTz4rKThTfZAK4CqreKmBZ4KHE+K1GA@xxxxxxxxxxxxxx/#t > > your change is different from what is proposed there, why? I didn’t notice this thread before I send this patch, I think the concept of my change is similar to Volodymyr Lisivka’s change, he/she introduced a separate variable for the PNP string length, I think it may be clearer and more readable than just “value += 2” Another thing that I am not too sure whether I am correct is this line of code DBG(dev, "1284 PNP String: %x %s\n", value, dev->pnp_string); What Volodymyr Lisivka changed is like this DBG(dev, "1284 PNP String: %x %s\n", pnp_length, dev->pnp_string); In my change, “value” equals to “pnp_length + 2” in Volodymyr Lisivka’s change, and I think we should print “the PNP string length + 2” instead of “the PNP string length”? > > thanks, > > greg k-h thanks, Wei Ming Chen
