From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751476AbaCVRjf (ORCPT ); Sat, 22 Mar 2014 13:39:35 -0400 Received: from mail-ee0-f53.google.com ([74.125.83.53]:56143 "EHLO mail-ee0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751325AbaCVRjc (ORCPT ); Sat, 22 Mar 2014 13:39:32 -0400 Message-ID: <532DCB06.9040601@googlemail.com> Date: Sat, 22 Mar 2014 18:40:22 +0100 From: =?ISO-8859-15?Q?Frank_Sch=E4fer?= User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: shuah.kh@samsung.com, m.chehab@samsung.com CC: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, shuahkhan@gmail.com Subject: Re: [PATCH] media: em28xx-video - change em28xx_scaler_set() to use em28xx_reg_len() References: <1395435890-15100-1-git-send-email-shuah.kh@samsung.com> <532D82C9.6010401@googlemail.com> <532DAAD0.6060209@samsung.com> In-Reply-To: <532DAAD0.6060209@samsung.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 22.03.2014 16:22, schrieb Shuah Khan: > 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 >>> --- >>> 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. Well, almost all register writes use a hardcoded length (most of the time it's 1). ;-) > > 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. Yes, if the length would be variable, then this would be a good idea. But AFAIK the length is always 2. > > 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 :) I'm more concerned about the fact that readers of the code could think that this is a write with a variable length, while the length is actually always the same. em28xx_reg_len() is a somewhat dirty hack for vidioc_[g,s]_register debugging ioctls only. Btw, what happens when you try to compile the code with this patch applied and CONFIG_VIDEO_ADV_DEBUG disabled ? ;-) Anyway, I very much appreciate your efforts to improve the em28xx driver. :-) There's much to do ! Regards, Frank > > -- Shuah >