linux-kernel - Re: [alsa-devel] [PATCH v4 08/15] soundwire: Add Slave status handling helpers

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Date:   Sun, 3 Dec 2017 21:07:29 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
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>, Mark <broonie@...nel.org>,
        Takashi <tiwai@...e.de>, 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: [alsa-devel] [PATCH v4 08/15] soundwire: Add Slave status
 handling helpers

On 12/3/17 11:08 AM, Vinod Koul wrote:
> On Fri, Dec 01, 2017 at 05:36:47PM -0600, Pierre-Louis Bossart wrote:
> 
>>> +/* called with bus_lock held */
>>> +static int sdw_get_device_num(struct sdw_slave *slave)
>>> +{
>>> +	int bit;
>>> +
>>> +	bit = find_first_zero_bit(slave->bus->assigned, SDW_MAX_DEVICES);
>>> +	if (bit == SDW_MAX_DEVICES) {
>>> +		bit = -ENODEV;
>>> +		goto err;
>>
>> My brain is starting to fry but is this correct? Bit11 seems like a valid
>> value. Should it be bit > 15 (assuming bit 12,13,14 are set to avoid using
>> groups and master)?
> 
> this is correct. You are confusing SDW concept and API return types!
> That should be hint for you to start weekend if you didn't do so :D
> 
> This API returns max value it was provided (last arg) if it doesn't
> find free bit. That's an indication to caller that we ran out of devices
> hence ENODEV error!

Can you just make sure bit11 is included?

> 
>>> +static int sdw_program_device_num(struct sdw_bus *bus)
>>> +{
>>> +	u8 buf[SDW_NUM_DEV_ID_REGISTERS] = {0};
>>> +	struct sdw_slave *slave, *_s;
>>> +	struct sdw_slave_id id;
>>> +	struct sdw_msg msg;
>>> +	bool found = false;
>>> +	int count = 0, ret;
>>> +	u64 addr;
>>> +
>>> +	/* No Slave, so use raw xfer api */
>>> +	ret = sdw_fill_msg(&msg, NULL, SDW_SCP_DEVID_0,
>>> +			SDW_NUM_DEV_ID_REGISTERS, 0, SDW_MSG_FLAG_READ, buf);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	do {
>>> +		ret = sdw_transfer(bus, NULL, &msg);
>>> +		if (ret == -ENODATA) { /* end of device id reads */
>>> +			ret = 0;
>>> +			break;
>>> +		}
>>> +		if (ret < 0) {
>>> +			dev_err(bus->dev, "DEVID read fail:%d\n", ret);
>>> +			break;
>>> +		}
>>> +
>>> +		/*
>>> +		 * 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_safe(slave, _s, &bus->slaves, node) {
>>> +			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");
>>> +		}
>>> +
>>> +		count++;
>>> +
>>> +	} while (ret == 0 && count < (SDW_MAX_DEVICES * 2));
>>
>> explain that the last condition is intentional - this is not a bug -, some
>> devices can drop off during enumeration and rejoin so might be counted
>> twice.
> 
> ok will add
>