linux-kernel - Re: [PATCH] regmap: Check for register readability before checking cache during read

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Message-ID: <274a7a7c-ca6c-44fe-8f7a-e19aaf86a86a@sirena.org.uk>
Date:   Thu, 15 Jun 2023 21:55:05 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Konrad Dybcio <konradybcio@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Bjorn Andersson <andersson@...nel.org>
Subject: Re: [PATCH] regmap: Check for register readability before checking
 cache during read

On Thu, Jun 15, 2023 at 10:45:53PM +0200, Konrad Dybcio wrote:
> On 13.06.2023 22:07, Mark Brown wrote:
> > Ensure that we don't return a spurious cache hit for unreadable registers
> > (eg, with the flat cache which doesn't understand sparseness) by checking
> > for readability before we do a cache lookup.

> this patch breaks using regmap_field_force_write() on fields that are
> parts of registers marked as write-only (e.g. by regmap_access_table.no_ranges)

> Is that intended?

> What's the recommended fix?

Ugh, let's just drop it - it's just an optimisation.

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