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SubjectRe: [PATCH v5 03/18] wlcore: simplify/fix/optimize reg_ch_conf_pending operations
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Paolo Bonzini <pbonzini@redhat.com> writes:

> On 15/03/19 00:16, Fenghua Yu wrote:
>> Hi, Valo,
>>
>> On Thu, Mar 14, 2019 at 03:16:33PM +0200, Kalle Valo wrote:
>>> Fenghua Yu <fenghua.yu@intel.com> writes:
>>>
>>>> From: Paolo Bonzini <pbonzini@redhat.com>
>>>>
>>>> Bitmaps are defined on unsigned longs, so the usage of u32[2] in the
>>>> wlcore driver is incorrect. As noted by Peter Zijlstra, casting arrays
>>>> to a bitmap is incorrect for big-endian architectures.
>>>>
>>>> When looking at it I observed that:
>>>>
>>>> - operations on reg_ch_conf_pending is always under the wl_lock mutex,
>>>> so set_bit is overkill
>>>>
>>>> - the only case where reg_ch_conf_pending is accessed a u32 at a time is
>>>> unnecessary too.
>>>>
>>>> This patch cleans up everything in this area, and changes tmp_ch_bitmap
>>>> to have the proper alignment.
>>>>
>>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>>> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
>>>
>>> [...]
>>>
>>>> int wlcore_cmd_regdomain_config_locked(struct wl1271 *wl)
>>>> {
>>>> struct wl12xx_cmd_regdomain_dfs_config *cmd = NULL;
>>>> int ret = 0, i, b, ch_bit_idx;
>>>> - u32 tmp_ch_bitmap[2];
>>>> + u32 tmp_ch_bitmap[2] __aligned(sizeof(unsigned long));
>>>> struct wiphy *wiphy = wl->hw->wiphy;
>>>> struct ieee80211_supported_band *band;
>>>> bool timeout = false;
>>>
>>> [...]
>>>
>>>> @@ -1754,8 +1751,8 @@ int wlcore_cmd_regdomain_config_locked(struct wl1271 *wl)
>>>> goto out;
>>>> }
>>>>
>>>> - cmd->ch_bit_map1 = cpu_to_le32(tmp_ch_bitmap[0]);
>>>> - cmd->ch_bit_map2 = cpu_to_le32(tmp_ch_bitmap[1]);
>>>> + cmd->ch_bit_map1 = tmp_ch_bitmap[0];
>>>> + cmd->ch_bit_map2 = tmp_ch_bitmap[1];
>>>
>>> Will sparse still be happy? AFAICS you are now assigning u32 to __le32:
>>>
>>> struct wl12xx_cmd_regdomain_dfs_config {
>>> struct wl1271_cmd_header header;
>>>
>>> __le32 ch_bit_map1;
>>> __le32 ch_bit_map2;
>>
>> Discussion between Peter and Paolo (https://lkml.org/lkml/2019/3/4/521)
>> may answer your question.
>
> No, Kalle is right. You do need to change
>
> - u32 tmp_ch_bitmap[2];
> + u32 tmp_ch_bitmap[2] __aligned(sizeof(unsigned long));
>
> into
>
> - u32 tmp_ch_bitmap[2];
> + __le32 tmp_ch_bitmap[2] __aligned(sizeof(unsigned long));
>
> The assignment from wl->reg_ch_conf_pending to tmp_ch_bitmap is fine
> because it goes through memcpy.

Thanks for confirming, I'll then drop patch 3 and wait for a new
version. IMHO it would be easier to submit this patch separately to
linux-wireless, no need to have within this bigger patchset.

--
Kalle Valo

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