linux-kernel - Re: [PATCH v5 06/17] soundwire: add support for sdw_slave

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Message-ID: <20191227070301.GK3006@vkoul-mobl>
Date:   Fri, 27 Dec 2019 12:33:01 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, gregkh@...uxfoundation.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [PATCH v5 06/17] soundwire: add support for sdw_slave_type

On 17-12-19, 15:03, Pierre-Louis Bossart wrote:
> In the existing SoundWire code, the bus does not have any explicit
> representation for Master Devices - only SoundWire Slaves are exposed.
> 
> In SoundWire, the Master Device provides the clock, synchronization
> information and command/control channels. When multiple links are
> supported, a Controller may expose more than one Master Device; they
> are typically embedded inside a larger audio cluster (be it in an
> SOC/chipset or an external audio codec), and we need to describe it
> using the Linux device and driver model.  This will allow for
> configuration functions to account for external dependencies such as
> power rails, clock sources or wake-up mechanisms. This transition will
> also allow for better sysfs support without the reference count issues
> mentioned in the initial reviews.
> 
> In this patch, we first convert the existing code to use an explicit
> sdw_slave_type and add error checks if this type is not set.
> 
> In follow-up patches we can add support for the sdw_master_type.
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> ---
>  drivers/soundwire/bus_type.c       | 23 ++++++++++++++++++-----
>  drivers/soundwire/slave.c          |  7 ++++++-
>  include/linux/soundwire/sdw_type.h |  6 ++++++
>  3 files changed, 30 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/soundwire/bus_type.c b/drivers/soundwire/bus_type.c
> index 9a0fd3ee1014..9719680a1e48 100644
> --- a/drivers/soundwire/bus_type.c
> +++ b/drivers/soundwire/bus_type.c
> @@ -49,13 +49,26 @@ int sdw_slave_modalias(const struct sdw_slave *slave, char *buf, size_t size)
>  
>  static int sdw_uevent(struct device *dev, struct kobj_uevent_env *env)
>  {
> -	struct sdw_slave *slave = to_sdw_slave_device(dev);
> +	struct sdw_slave *slave;
>  	char modalias[32];
>  
> -	sdw_slave_modalias(slave, modalias, sizeof(modalias));
> -
> -	if (add_uevent_var(env, "MODALIAS=%s", modalias))
> -		return -ENOMEM;
> +	if (is_sdw_slave(dev)) {
> +		slave = to_sdw_slave_device(dev);
> +
> +		sdw_slave_modalias(slave, modalias, sizeof(modalias));
> +
> +		if (add_uevent_var(env, "MODALIAS=%s", modalias))
> +			return -ENOMEM;
> +	} else {
> +		/*
> +		 * We only need to handle uevents for the Slave device
> +		 * type. This error cannot happen unless the .uevent
> +		 * callback is set to use this function for a
> +		 * different device type (e.g. Master or Monitor)
> +		 */
> +		dev_err(dev, "uevent for unknown Soundwire type\n");
> +		return -EINVAL;

At this point and after next patch, the above code would be a no-op, do
we want this here, if so why?

-- 
~Vinod