Re: [PATCH] ath9k_htc: avoid memcpy when downloading firmware

From: Fred Chou
Date: Tue Mar 03 2015 - 09:41:06 EST




On 3/3/2015 2:00 PM, Eric Dumazet wrote:
> On Tue, 2015-03-03 at 12:24 +0800, Fred Chou wrote:
>> From: Fred Chou <fred.chou.nd@xxxxxxxxx>
>>
>> The temporary buffer to hold firmware data is not really needed,
>> and memcpy can be avoided by using data pointer instead.
>>
>> Signed-off-by: Fred Chou <fred.chou.nd@xxxxxxxxx>
>> ---
>> drivers/net/wireless/ath/ath9k/hif_usb.c | 12 ++----------
>> 1 file changed, 2 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
>> index 10c02f5..0bc35a8 100644
>> --- a/drivers/net/wireless/ath/ath9k/hif_usb.c
>> +++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
>> @@ -986,30 +986,22 @@ static int ath9k_hif_usb_download_fw(struct hif_device_usb *hif_dev)
>> const void *data = hif_dev->fw_data;
>
> Here data can be vmalloc() backed.
>
>> size_t len = hif_dev->fw_size;
>> u32 addr = AR9271_FIRMWARE;
>> - u8 *buf = kzalloc(4096, GFP_KERNEL);
>
> Here buf is kmalloc() backed.
>
>> u32 firm_offset;
>>
>> - if (!buf)
>> - return -ENOMEM;
>> -
>> while (len) {
>> transfer = min_t(size_t, len, 4096);
>> - memcpy(buf, data, transfer);
>>
>> err = usb_control_msg(hif_dev->udev,
>> usb_sndctrlpipe(hif_dev->udev, 0),
>> FIRMWARE_DOWNLOAD, 0x40 | USB_DIR_OUT,
>> - addr >> 8, 0, buf, transfer, HZ);
>
>
> Are you sure usb_control_msg() accepts vmalloc()ed buffers ?
>
> My guess is the answer is no.
>
>

I agree, and I would like to drop the patch. Thanks.
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