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

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Date:   Thu, 19 Oct 2017 10:54:50 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        ALSA <alsa-devel@...a-project.org>,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Sudheer Papothi <spapothi@...eaurora.org>, plai@...eaurora.org,
        LKML <linux-kernel@...r.kernel.org>,
        Pierre <pierre-louis.bossart@...ux.intel.com>,
        patches.audio@...el.com, Mark <broonie@...nel.org>,
        srinivas.kandagatla@...aro.org, Shreyas NC <shreyas.nc@...el.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Sagar Dharia <sdharia@...eaurora.org>, alan@...ux.intel.com
Subject: Re: [alsa-devel] [PATCH 03/14] soundwire: Add Master registration

On Thu, 19 Oct 2017 05:03:19 +0200,
Vinod Koul wrote:
> 
> +/**
> + * sdw_add_bus_master: add a bus Master instance
> + *
> + * @bus: bus instance
> + *
> + * Initializes the bus instance, read properties and create child
> + * devices.
> + */
> +int sdw_add_bus_master(struct sdw_bus *bus)
> +{
> +	int ret;
> +
> +	if (!bus->dev) {
> +		pr_err("SoundWire bus has no device");
> +		return -ENODEV;
> +	}
> +
> +	mutex_init(&bus->bus_lock);
> +	INIT_LIST_HEAD(&bus->slaves);
> +
> +	/*
> +	 * 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)

The bus->dev NULL check is already done at the beginning of the
function, so here are superfluous.


> +static int sdw_delete_slave(struct device *dev, void *data)
> +{
> +	struct sdw_slave *slave = dev_to_sdw_dev(dev);
> +	struct sdw_bus *bus = slave->bus;
> +
> +	mutex_lock(&bus->bus_lock);
> +	if (!list_empty(&bus->slaves))
> +		list_del(&slave->node);

You can perform list_del_init() without empty check.

> +void sdw_extract_slave_id(struct sdw_bus *bus,
> +			unsigned long long addr, struct sdw_slave_id *id)

Use u64 instead.

> +{
> +	dev_dbg(bus->dev, "SDW Slave Addr: %llx", addr);
> +
> +	/*
> +	 * Spec definition
> +	 *   Register		Bit	Contents
> +	 *   DevId_0 [7:4]	47:44	sdw_version
> +	 *   DevId_0 [3:0]	43:40	unique_id
> +	 *   DevId_1		39:32	mfg_id [15:8]
> +	 *   DevId_2		31:24	mfg_id [7:0]
> +	 *   DevId_3		23:16	part_id [15:8]
> +	 *   DevId_4		15:08	part_id [7:0]
> +	 *   DevId_5		07:00	class_id
> +	 */
> +	id->sdw_version = (addr >> 44) & GENMASK(3, 0);
> +	id->unique_id = (addr >> 40) & GENMASK(3, 0);
> +	id->mfg_id = (addr >> 24) & GENMASK(15, 0);
> +	id->part_id = (addr >> 8) & GENMASK(15, 0);
> +	id->class_id = addr & GENMASK(7, 0);
> +
> +	dev_info(bus->dev,
> +		"SDW Slave class_id %x, part_id %x, mfg_id %x, unique_id %x, version %x",
> +				id->class_id, id->part_id, id->mfg_id,
> +				id->unique_id, id->sdw_version);
> +

Do we want to print a message always at each invocation?

> +static int sdw_slave_add(struct sdw_bus *bus,
> +		struct sdw_slave_id *id, struct fwnode_handle *fwnode)
> +{
> +	struct sdw_slave *slave;
> +	char name[32];
> +	int ret;
> +
> +	slave = kzalloc(sizeof(*slave), GFP_KERNEL);
> +	if (!slave)
> +		return -ENOMEM;
> +
> +	/* Initialize data structure */
> +	memcpy(&slave->id, id, sizeof(*id));
> +
> +	/* name shall be sdw:link:mfg:part:class:unique */
> +	snprintf(name, sizeof(name), "sdw:%x:%x:%x:%x:%x",
> +			bus->link_id, id->mfg_id, id->part_id,
> +			id->class_id, id->unique_id);

You can set the name directly via dev_set_name().  It's printf format,
after all.

> +	slave->dev.parent = bus->dev;
> +	slave->dev.fwnode = fwnode;
> +	dev_set_name(&slave->dev, "%s", name);
> +	slave->dev.release = sdw_slave_release;
> +	slave->dev.bus = &sdw_bus_type;
> +	slave->bus = bus;
> +	slave->status = SDW_SLAVE_UNATTACHED;
> +	slave->dev_num = 0;
> +
> +	mutex_lock(&bus->bus_lock);
> +	list_add_tail(&slave->node, &bus->slaves);
> +	mutex_unlock(&bus->bus_lock);
> +
> +	ret = device_register(&slave->dev);
> +	if (ret) {
> +		dev_err(bus->dev, "Failed to add slave: ret %d\n", ret);
> +
> +		/*
> +		 * On err, don't free but drop ref as this will be freed
> +		 * when release method is invoked.
> +		 */
> +		put_device(&slave->dev);

Wouldn't it leave a stale link to bus?


thanks,

Takashi