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SubjectRe: [PATCH] media: em28xx-video - change em28xx_scaler_set() to use em28xx_reg_len()
On 03/22/2014 06:32 AM, Frank Schäfer wrote:
>
> Am 21.03.2014 22:04, schrieb Shuah Khan:
>> Change em28xx_scaler_set() to use em28xx_reg_len() to get register
>> lengths for EM28XX_R30_HSCALELOW and EM28XX_R32_VSCALELOW registers,
>> instead of hard-coding the length. Moved em28xx_reg_len() definition
>> for it to be visible to em28xx_scaler_set().
>>
>> Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
>> ---
>> drivers/media/usb/em28xx/em28xx-video.c | 29 ++++++++++++++++-------------
>> 1 file changed, 16 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c
>> index 19af6b3..f8a91de 100644
>> --- a/drivers/media/usb/em28xx/em28xx-video.c
>> +++ b/drivers/media/usb/em28xx/em28xx-video.c
>> @@ -272,6 +272,18 @@ static void em28xx_capture_area_set(struct em28xx *dev, u8 hstart, u8 vstart,
>> }
>> }
>>
>> +static int em28xx_reg_len(int reg)
>> +{
>> + switch (reg) {
>> + case EM28XX_R40_AC97LSB:
>> + case EM28XX_R30_HSCALELOW:
>> + case EM28XX_R32_VSCALELOW:
>> + return 2;
>> + default:
>> + return 1;
>> + }
>> +}
>> +
>> static int em28xx_scaler_set(struct em28xx *dev, u16 h, u16 v)
>> {
>> u8 mode;
>> @@ -284,11 +296,13 @@ static int em28xx_scaler_set(struct em28xx *dev, u16 h, u16 v)
>>
>> buf[0] = h;
>> buf[1] = h >> 8;
>> - em28xx_write_regs(dev, EM28XX_R30_HSCALELOW, (char *)buf, 2);
>> + em28xx_write_regs(dev, EM28XX_R30_HSCALELOW, (char *)buf,
>> + em28xx_reg_len(EM28XX_R30_HSCALELOW));
>>
>> buf[0] = v;
>> buf[1] = v >> 8;
>> - em28xx_write_regs(dev, EM28XX_R32_VSCALELOW, (char *)buf, 2);
>> + em28xx_write_regs(dev, EM28XX_R32_VSCALELOW, (char *)buf,
>> + em28xx_reg_len(EM28XX_R32_VSCALELOW));
> Hmm... registers 0x30 and 0x32 are always 2 bytes long.
> So this change would needlessly complicate the code.
>

The reason I made the change is that em28xx_reg_len() is handling these
two registers and I thought it would be good to make it consistent with
other writes to these registers and not hard-code the length.

I think it would help with maintenance later by avoiding hard-coding the
length and use the existing routine that returns the length for these
registers.

You are correct that it does add a function call in the code path. So if
you think the trade-off isn't worth it, I am not going to argue with it :)

-- Shuah

--
Shuah Khan
Senior Linux Kernel Developer - Open Source Group
Samsung Research America(Silicon Valley)
shuah.kh@samsung.com | (970) 672-0658
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