Re: [PATCH v4 6/7] usb: gadget: uvc: add VIDIOC function

[kernel test robot <lkp@xxxxxxxxx>]

Hi Michael,

I love your patch! Perhaps something to improve:

[auto build test WARNING on media-tree/master]
[also build test WARNING on usb/usb-testing peter-chen-usb/for-usb-next v5.16-rc4 next-20211206]
[cannot apply to balbi-usb/testing/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Michael-Grzeschik/usb-gadget-uvc-use-configfs-entries-for-negotiation-and-v4l2-VIDIOCS/20211206-070014
base:   git://linuxtv.org/media_tree.git master
config: riscv-randconfig-r024-20211205 (https://download.01.org/0day-ci/archive/20211206/202112061923.TiElYqbE-lkp@xxxxxxxxx/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 6e8678903523019903222e4521a5e41af743cab0)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://github.com/0day-ci/linux/commit/fddc809d40b686678ad8bea9c47f37b355b3608b
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Michael-Grzeschik/usb-gadget-uvc-use-configfs-entries-for-negotiation-and-v4l2-VIDIOCS/20211206-070014
        git checkout fddc809d40b686678ad8bea9c47f37b355b3608b
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/usb/gadget/function/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> drivers/usb/gadget/function/uvc_v4l2.c:73:2: warning: variable 'uformat' is used uninitialized whenever 'for' loop exits because its condition is false [-Wsometimes-uninitialized]
           list_for_each_entry(format, &uvc->header->formats, entry) {
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/list.h:631:7: note: expanded from macro 'list_for_each_entry'
                !list_entry_is_head(pos, head, member);                    \
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/usb/gadget/function/uvc_v4l2.c:81:9: note: uninitialized use occurs here
           return uformat;
                  ^~~~~~~
   drivers/usb/gadget/function/uvc_v4l2.c:73:2: note: remove the condition if it is always true
           list_for_each_entry(format, &uvc->header->formats, entry) {
           ^
   include/linux/list.h:631:7: note: expanded from macro 'list_for_each_entry'
                !list_entry_is_head(pos, head, member);                    \
                ^
   drivers/usb/gadget/function/uvc_v4l2.c:70:29: note: initialize the variable 'uformat' to silence this warning
           struct uvcg_format *uformat;
                                      ^
                                       = NULL
   drivers/usb/gadget/function/uvc_v4l2.c:112:2: warning: variable 'uformat' is used uninitialized whenever 'for' loop exits because its condition is false [-Wsometimes-uninitialized]
           list_for_each_entry(format, &uvc->header->formats, entry) {
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/list.h:631:7: note: expanded from macro 'list_for_each_entry'
                !list_entry_is_head(pos, head, member);                    \
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/usb/gadget/function/uvc_v4l2.c:121:9: note: uninitialized use occurs here
           return uformat;
                  ^~~~~~~
   drivers/usb/gadget/function/uvc_v4l2.c:112:2: note: remove the condition if it is always true
           list_for_each_entry(format, &uvc->header->formats, entry) {
           ^
   include/linux/list.h:631:7: note: expanded from macro 'list_for_each_entry'
                !list_entry_is_head(pos, head, member);                    \
                ^
   drivers/usb/gadget/function/uvc_v4l2.c:110:29: note: initialize the variable 'uformat' to silence this warning
           struct uvcg_format *uformat;
                                      ^
                                       = NULL
   2 warnings generated.


vim +73 drivers/usb/gadget/function/uvc_v4l2.c

    66	
    67	struct uvcg_format *find_format_by_index(struct uvc_device *uvc, int index)
    68	{
    69		struct uvcg_format_ptr *format;
    70		struct uvcg_format *uformat;
    71		int i = 1;
    72	
  > 73		list_for_each_entry(format, &uvc->header->formats, entry) {
    74			if (index == i) {
    75				uformat = format->fmt;
    76				break;
    77			}
    78			i++;
    79		}
    80	
    81		return uformat;
    82	}
    83	

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