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From: Philipp Zabel <p.zabel@pengutronix.de>
To: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
Cc: Steve Longerbeam <slongerbeam@gmail.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	linux-media@vger.kernel.org, linux-staging@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, kernel@puri.sm,
	phone-devel@vger.kernel.org
Subject: Re: [PATCH] media: imx: Round line size to 4 bytes
Date: Mon, 18 Oct 2021 12:21:15 +0200	[thread overview]
Message-ID: <b99705233d4a79c22d99c41568477491a51f48c6.camel@pengutronix.de> (raw)
In-Reply-To: <20211017130713.4668c616.dorota.czaplejewicz@puri.sm>

On Sun, 2021-10-17 at 13:07 +0200, Dorota Czaplejewicz wrote:
> Hello,
> 
> On Thu, 14 Oct 2021 13:26:26 +0200
> Philipp Zabel <p.zabel@pengutronix.de> wrote:
> 
> > Hi Dorota,
> > 
> > On Wed, 2021-10-13 at 11:26 +0200, Dorota Czaplejewicz wrote:
> > > On Fri, 08 Oct 2021 14:19:41 +0200 Philipp Zabel <p.zabel@pengutronix.de> wrote:  
> > [...]
> > > > I wonder: if you use 4-byte aligned width and odd height, does the CSI
> > > > write over the end of the buffer?  
> > > 
> > > I tested this case, and found a glitch which suggests the last 4 bytes are ignored:
> > > 
> > > https://source.puri.sm/Librem5/linux-next/uploads/cfb59e3832431aaa3a69549455502568/image.png  
> > 
> > Thank you for testing, so it appears that at least without FBUF_STRIDE
> > the only requirement is that the whole image size must be a multiple of
> > 8 bytes.
> > 
> > > That would be taken care of rounding up towards a number decided at runtime, like:
> > > 
> > > divisor = 8 >> (mbus->height % 2);  
> > 
> > Which would then cause the CSI to write past the end of the buffer?
> > 
> I'm not sure if you point out the mistake here (should be "4 <<"), or
> the fact that rounding is happening. If it's the latter, then it's of
> no concern: the values derived here are used to calculate buffer size.
> 
> I'm submitting a new series where this is fixed.

Thanks, I just didn't understand your intention. The name "divisor"
threw me off, see the comment in the new series.

regards
Philipp

      reply	other threads:[~2021-10-18 10:21 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-06 11:05 Dorota Czaplejewicz
2021-10-08 12:19 ` Philipp Zabel
2021-10-13  9:26   ` Dorota Czaplejewicz
2021-10-14 11:26     ` Philipp Zabel
2021-10-17 11:07       ` Dorota Czaplejewicz
2021-10-18 10:21         ` Philipp Zabel [this message]

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