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From:   Stefan Binding <sbinding@opensource.cirrus.com>
To:     "Rafael J . Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>, Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>
CC:     <linux-acpi@vger.kernel.org>, <alsa-devel@alsa-project.org>,
        <linux-kernel@vger.kernel.org>, <patches@opensource.cirrus.com>,
        "Stefan Binding" <sbinding@opensource.cirrus.com>
Subject: [PATCH v6 0/2] Read _SUB from ACPI to be able to identify firmware
Date:   Thu, 7 Jul 2022 16:10:35 +0100
Message-ID: <20220707151037.3901050-1-sbinding@opensource.cirrus.com>
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Precedence: bulk

CS35L41 has a DSP which is able to run firmware, as well as a tuning file.
Different systems may want to use different firmwares and tuning files, and
some firmwares/tunings may not be compatible with other systems.
To allow a system to select the correct fimware/tuning, we can read an _SUB
from the ACPI. This _SUB can then be used to uniquely identify the system
in the firmware/tuning file name.

Add a helper function which reads the _SUB, so this can be used by other
parts in the future.
Add support inside the CS35L41 ASoC driver to read this _SUB, and save it
appropriately.

Changes since v5:
- Clean up return codes
- Refactor length calculation
- Allow fallback to existing behaviour when bad ACPI is detected

Changes since v4:
- Rename function

Changes since v3:
- Fix 32 bit format string warning

Changes since v2:
- Fix error in function prototype

Changes since v1:
- Add length validation for SSID String
- Rename API
- Allocate memory inside API
- Use ACPI_HANDLE macro instead of ACPI_COMPANION
- Improve error handling

Stefan Binding (2):
  ACPI: utils: Add api to read _SUB from ACPI
  ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

 drivers/acpi/utils.c       | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h       |  6 ++++++
 sound/soc/codecs/cs35l41.c | 30 ++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+)

-- 
2.25.1