linux-kernel - Re: [alsa-devel] [PATCH 08/14] soundwire: Add Slave status handling helpers

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Date:   Thu, 19 Oct 2017 15:44:12 +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 08/14] soundwire: Add Slave status handling    helpers

On Thu, 19 Oct 2017 05:03:24 +0200,
Vinod Koul wrote:
> 
> +static struct sdw_slave *sdw_get_slave(struct sdw_bus *bus, int i)
> +{
> +	struct sdw_slave *slave;
> +
> +	list_for_each_entry(slave, &bus->slaves, node) {
> +		if (slave->dev_num == i)
> +			return slave;
> +	}
> +
> +	return NULL;

Is this performed always in bus_lock, right?
Better to document it.

> +static int sdw_compare_devid(struct sdw_slave *slave, struct sdw_slave_id id)
> +{
> +
> +	if ((slave->id.unique_id != id.unique_id) ||
> +			(slave->id.mfg_id != id.mfg_id) ||
> +			(slave->id.part_id != id.part_id) ||
> +			(slave->id.class_id != id.class_id))

Align indentations.

> +static int sdw_get_device_num(struct sdw_slave *slave)
> +{
> +	bool assigned = false;
> +	int i;
> +
> +	mutex_lock(&slave->bus->bus_lock);
> +	for (i = 1; i <= SDW_MAX_DEVICES; i++) {
> +		if (slave->bus->assigned[i] == true)
> +			continue;
> +
> +		slave->bus->assigned[i] = true;
> +		assigned = true;
> +
> +		/*
> +		 * Do not update dev_num in Slave data structure here,
> +		 * Update once program dev_num is successful
> +		 */
> +		break;

With the bitmap, it's easier, you can use find_next_zero_bit() :)


> +static int sdw_program_device_num(struct sdw_bus *bus)
> +{
> +	u8 buf[SDW_NUM_DEV_ID_REGISTERS] = {0};
> +	unsigned long long addr;

Use u64.

> +	struct sdw_slave *slave;
> +	struct sdw_slave_id id;
> +	struct sdw_msg msg;
> +	bool found = false;
> +	int ret;
> +
> +	/* No Slave, so use raw xfer api */
> +	sdw_fill_msg(&msg, SDW_SCP_DEVID_0, SDW_NUM_DEV_ID_REGISTERS,
> +					0, SDW_MSG_FLAG_READ, buf);
> +
> +	do {
> +		ret = sdw_transfer(bus, NULL, &msg);
> +		if (ret == -ENODATA)
> +			break;
> +		if (ret < 0) {
> +			dev_err(bus->dev, "DEVID read fail:%d\n", ret);
> +			break;

So here we break, and the function returns zero.  Is this the expected
behavior?

> +		}
> +
> +		/*
> +		 * Construct the addr and extract. Cast the higher shift
> +		 * bits to avoid truncation due to size limit.
> +		 */
> +		addr = buf[5] | (buf[4] << 8) | (buf[3] << 16) |
> +			(buf[2] << 24) | ((unsigned long long)buf[1] << 32) |
> +			((unsigned long long)buf[0] << 40);
> +
> +		sdw_extract_slave_id(bus, addr, &id);
> +
> +		/* Now compare with entries */
> +		list_for_each_entry(slave, &bus->slaves, node) {

Isn't this function protected under bus_lock...?

> +			if (sdw_compare_devid(slave, id) == 0) {
> +				found = true;
> +
> +				/*
> +				 * Assign a new dev_num to this Slave and
> +				 * not mark it present. It will be marked
> +				 * present after it reports ATTACHED on new
> +				 * dev_num
> +				 */
> +				ret = sdw_assign_device_num(slave);
> +				if (ret) {
> +					dev_err(slave->bus->dev,
> +						"Assign dev_num failed:%d",
> +						ret);
> +					return ret;
> +				}
> +
> +				break;
> +			}
> +		}
> +
> +		if (found == false) {
> +			/* TODO: Park this device in Group 13 */
> +			dev_err(bus->dev, "Slave Entry not found");

No break here?  Otherwise...

> +		}
> +
> +	} while (ret == 0);

... the outer loop may go endlessly.
This condition doesn't look effective.

> +
> +	return 0;

... and here returns no error?


thanks,

Takashi