Re: [PATCH v3 2/6] usb:common Separated decoding functions from dwc3 driver.
From: Greg KH
Date: Mon Feb 04 2019 - 06:45:08 EST
On Thu, Jan 31, 2019 at 11:52:29AM +0000, Pawel Laszczak wrote:
> Patch moves some decoding functions from driver/usb/dwc3/debug.h driver
> to driver/usb/common/debug.c file. These moved functions include:
> These functions are used also in inroduced cdns3 driver.
> All functions prefixes were changed from dwc3 to usb.
> Also, function's parameters has been extended according to the name
> of fields in standard SETUP packet.
> Additionally, patch adds usb_decode_ctrl function to
> include/linux/usb/ch9.h file.
Why ch9.h? It's not something that is specified in the spec, it's a
usb-specific thing :)
Also, the api for that function is not ok. If you are going to make
this something that the whole kernel can call, you have to fix it up:
> + * usb_decode_ctrl - Returns human readable representation of control request.
> + * @str: buffer to return a human-readable representation of control request.
> + * This buffer should have about 200 bytes.
"about 200 bytes" is not very specific.
Pass in the length so we know we don't overflow it.
> + * @bRequestType: matches the USB bmRequestType field
> + * @bRequest: matches the USB bRequest field
> + * @wValue: matches the USB wValue field (CPU byte order)
> + * @wIndex: matches the USB wIndex field (CPU byte order)
> + * @wLength: matches the USB wLength field (CPU byte order)
> + *
> + * Function returns decoded, formatted and human-readable description of
> + * control request packet.
> + *
> + * Important: wValue, wIndex, wLength parameters before invoking this function
> + * should be processed by le16_to_cpu macro.
> + */
> +const char *usb_decode_ctrl(char *str, __u8 bRequestType, __u8 bRequest,
> + __u16 wValue, __u16 wIndex, __u16 wLength);
Why are you returning a value, isn't the data stored in str? Why not
just return an int saying if the call succeeded or not?