linux-kernel - Re: [PATCH v4 0/13] dmaengine: introduce sg_nents_for

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Message-ID: <aV9S2oAsIIIZoYnR@smile.fi.intel.com>
Date: Thu, 8 Jan 2026 08:46:50 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Vinod Koul <vkoul@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Stefan Wahren <wahrenst@....net>,
	Thomas Andreatta <thomasandreatta2000@...il.com>,
	Caleb Sander Mateos <csander@...estorage.com>,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
	Olivier Dautricourt <olivierdautricourt@...il.com>,
	Stefan Roese <sr@...x.de>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
	Daniel Mack <daniel@...que.org>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Lizhi Hou <lizhi.hou@....com>, Brian Xu <brian.xu@....com>,
	Raj Kumar Rampelli <raj.kumar.rampelli@....com>,
	Michal Simek <michal.simek@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v4 0/13] dmaengine: introduce sg_nents_for_dma() and
 convert users

On Tue, Dec 16, 2025 at 06:41:44PM +0530, Vinod Koul wrote:
> On 24-11-25, 13:09, Andy Shevchenko wrote:
> > A handful of the DMAengine drivers use same routine to calculate the number of
> > SG entries needed for the given DMA transfer. Provide a common helper for them
> > and convert.
> > 
> > I left the new helper on SG level of API because brief grepping shows potential
> > candidates outside of DMA engine, e.g.:
> > 
> >   drivers/crypto/chelsio/chcr_algo.c:154:  nents += DIV_ROUND_UP(less, entlen);
> >   drivers/spi/spi-stm32.c:1495:  /* Count the number of entries needed */
> > 
> > Changelog v4:
> > - fixed compilation errors (Vinod)
> 
> :-(
> 
> drivers/dma/altera-msgdma.c: In function ‘msgdma_prep_slave_sg’:
> drivers/dma/altera-msgdma.c:399:29: error: unused variable ‘sg’ [-Werror=unused-variable]
> 
> Clearly your script is not working. I am surprised that you are not able
> to compile these changes. Bit disappointed tbh!

This is W=1 build with WERROR=y, yet I agree that I must have tested this as
well. Sorry, I will do v5 with carefully tested all modules to be compiled
with `make W=1`.

-- 
With Best Regards,
Andy Shevchenko