linux-kernel - Re: [PATCH 03/14] soundwire: Add Master registration

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Message-ID: <20171021091230.pwevgreloynqe7nu@sirena.org.uk>
Date:   Sat, 21 Oct 2017 10:12:30 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        ALSA <alsa-devel@...a-project.org>, Takashi <tiwai@...e.de>,
        Pierre <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Shreyas NC <shreyas.nc@...el.com>, patches.audio@...el.com,
        alan@...ux.intel.com,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Sagar Dharia <sdharia@...eaurora.org>,
        srinivas.kandagatla@...aro.org, plai@...eaurora.org,
        Sudheer Papothi <spapothi@...eaurora.org>
Subject: Re: [PATCH 03/14] soundwire: Add Master registration

On Thu, Oct 19, 2017 at 08:33:19AM +0530, Vinod Koul wrote:

> +	/*
> +	 * SDW is an enumerable bus, but devices can be powered off. So,
> +	 * they won't be able to report as present.
> +	 *
> +	 * Create Slave devices based on Slaves described in
> +	 * the respective firmware (ACPI/DT)
> +	 */
> +
> +	if (IS_ENABLED(CONFIG_ACPI) && bus->dev && ACPI_HANDLE(bus->dev))
> +		ret = sdw_acpi_find_slaves(bus);
> +	else if (IS_ENABLED(CONFIG_OF) && bus->dev && bus->dev->of_node)
> +		ret = sdw_of_find_slaves(bus);
> +	else
> +		ret = -ENOTSUPP; /* No ACPI/DT so error out */

Devices *can* be powered off but is there any reason that a system
couldn't be designed with them always powered?  Also given that we don't
actually have any DT support the stubs for it are at best misleading,
it's not going to be hard for someone to add them later.

> +	mutex_lock(&bus->bus_lock);
> +	if (!list_empty(&bus->slaves))
> +		list_del(&slave->node);

Shouldn't that be a while?  Or at least warn if there's anything extra
there.  The code just looks very wrong as is.

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