linux-kernel - Re: [PATCH] iio: amplifiers: ada4250: use DMA-safe memory for regmap_bulk

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Message-ID: <aAO7Lw13xrEGmZLL@smile.fi.intel.com>
Date: Sat, 19 Apr 2025 18:03:11 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Antoniu Miclaus <antoniu.miclaus@...log.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Nuno Sá <nuno.sa@...log.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: amplifiers: ada4250: use DMA-safe memory for
 regmap_bulk_read()

On Fri, Apr 18, 2025 at 02:09:04PM -0500, David Lechner wrote:
> On 4/18/25 1:58 PM, Andy Shevchenko wrote:
> > пʼятниця, 18 квітня 2025 р. David Lechner <dlechner@...libre.com <mailto:dlechner@...libre.com>> пише:
> > 
> >     Use DMA-safe memory instead of stack-allocated memory for the call to
> >     regmap_bulk_read() in the ada4250_init() function as this could be used
> >     directly by a SPI controller.
> > 
> > Sorry, but can you elaborate more on this? If driver doesn’t override the
> > callbacks the regmap SPI uses spi_write_then_read() which is supposed to be
> > dma safe. 
> 
> Ah, I didn't dig that far down. Will send a new patch that just cleans up the
> unnecessary alignment and unaligned call.

But do you have a real life issue with that? Coincidentally we discussed
similar case in another driver with colleague of mine, and he insists that it
might be still broken (somewhere).

> (Also can't believe you sent HTML mail!)

Yeah, Gmail from the phone can't actually send a plain text :-(
Very strange from Google, while I understand that the case most
likely is for business, where HTML is a standard (sic!) for emails.

-- 
With Best Regards,
Andy Shevchenko