Re: [PATCH] staging: rtl8723au: Fix sparse warnings

Krzysztof Konopko
2014-12-12T22:30:30Z

On 12/12/14 17:43, Larry Finger wrote:
> On 12/12/2014 06:52 AM, Dan Carpenter wrote:
>> On Thu, Dec 11, 2014 at 05:53:30PM -0600, Larry Finger wrote:
>>> On 12/11/2014 04:23 PM, Krzysztof Konopko wrote:
>>>> Some struct fields in wifi.h are meant to be __le16 bu were declared as
>>>> unsigned short. This was reported by sparse:
>>>>
>>>> rtw_wlan_util.c:538:24: warning: cast to restricted __le16
>>>> rtw_wlan_util.c:1544:29: warning: cast to restricted __le16
>>>> rtw_wlan_util.c:1546:25: warning: cast to restricted __le16
>>>>
>>>> This patch changes declared types of the struct fields involved.
>>>>
>>>> Signed-off-by: Krzysztof Konopko <kris@konagma.com>
>>>> ---
>>>> drivers/staging/rtl8723au/include/wifi.h | 6 +++---
>>>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/staging/rtl8723au/include/wifi.h
>>>> b/drivers/staging/rtl8723au/include/wifi.h
>>>> index fd3da3b..8a2adc5 100644
>>>> --- a/drivers/staging/rtl8723au/include/wifi.h
>>>> +++ b/drivers/staging/rtl8723au/include/wifi.h
>>>> @@ -28,7 +28,7 @@
>>>> struct AC_param {
>>>> unsigned char ACI_AIFSN;
>>>> unsigned char CW;
>>>> - unsigned short TXOP_limit;
>>>> + __le16 TXOP_limit;
>>>> } __packed;
>>>>
>>>> struct WMM_para_element {
>>>> @@ -39,9 +39,9 @@ struct WMM_para_element {
>>>>
>>>> struct ADDBA_request {
>>>> unsigned char dialog_token;
>>>> - unsigned short BA_para_set;
>>>> + __le16 BA_para_set;
>>>> unsigned short BA_timeout_value;
>>>> - unsigned short BA_starting_seqctrl;
>>>> + __le16 BA_starting_seqctrl;
>>>> } __packed;
>>>
>>> This fix may make the sparse warnings go away, but I think it
>>> introduces new bugs.
>>
>> This kind of change, doesn't change the compiled code only how Sparse
>> sees it. It can't introduce bugs.
>>
>> But it may well be that the calls to le16_to_cpu() should be removed. I
>> looked at it a bit but I don't know.
>
> Your point regarding bugs is taken. What I should have said is that
> blindly making _le changes to hide Sparse messages may hide existing
> bugs for BE hardware.
>
> Larry
>
>

Yes, I started it off blindly but dug further and now have a better
understanding. Looking in ieee80211.h and getting your feedback helped
me to get a better understanding of the situation.

I see nothing wrong in declaring data that is supposed to be
little-endian as __le. You say that making these changes blindly may
hide existing bugs but:

* not doing anything about it is not helpful either

* this is no longer changing anything blindly
Relevant structs: `addba_req` and `ieee80211_wmm_ac_param` do declare
their fields as __le where needed.

I do take a point though about making this change inconsistently
(blindly) in my initial patch.

Kris