linux-kernel - Re: [PATCH 02/14] soundwire: Add SoundWire bus type

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Date:   Fri, 20 Oct 2017 10:41:01 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        ALSA <alsa-devel@...a-project.org>, Mark <broonie@...nel.org>,
        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 02/14] soundwire: Add SoundWire bus type

On Thu, Oct 19, 2017 at 09:40:06AM +0200, Takashi Iwai wrote:
> On Thu, 19 Oct 2017 05:03:18 +0200,
> Vinod Koul wrote:
> > +
> > +config SOUNDWIRE_BUS
> > +	tristate
> > +	default SOUNDWIRE
> > +
> 
> Does it make sense to be tristate?
> Since CONFIG_SOUNDWIRE is a bool, the above would be also only either
> Y or N.  If it's Y and others select M, it'll be still Y.

hmmm good point. I think would make sense to make SOUNDWIRE as tristate too,
just like SOUND :)

> > + * sdw_get_device_id: find the matching SoundWire device id
> > + *
> > + * @slave: SoundWire Slave device
> > + * @drv: SoundWire Slave Driver
> 
> Inconsistent upper/lower letters in these two lines.

thanks for spotting, will fix

> > + * The match is done by comparing the mfg_id and part_id from the
> > + * struct sdw_device_id. class_id is unused, as it is a placeholder
> > + * in MIPI Spec.
> > + */
> > +static const struct sdw_device_id *
> > +sdw_get_device_id(struct sdw_slave *slave, struct sdw_driver *drv)
> > +{
> > +	const struct sdw_device_id *id = drv->id_table;
> > +
> > +	while (id && id->mfg_id) {
> > +		if (slave->id.mfg_id == id->mfg_id &&
> > +				slave->id.part_id == id->part_id) {
> 
> Please indentation properly.

what do you advise?

		if (slave->id.mfg_id == id->mfg_id &&
			slave->id.part_id == id->part_id) {

would mean below one is at same indent. Some people use:

		if (slave->id.mfg_id == id->mfg_id &&
		   slave->id.part_id == id->part_id) {

Is it Documented anywhere...


> 
> > +			return id;
> > +		}
> 
> Superfluous braces for a single-line.

That bit was intentional. Yes it is not required but given that if condition
was falling to two lines, I wanted to help readability by adding these. I can
remove them..

> 
> > +		id++;
> > +	}
> > +
> > +	return NULL;
> > +}
> > +
> > +static int sdw_bus_match(struct device *dev, struct device_driver *ddrv)
> > +{
> > +	struct sdw_slave *slave = dev_to_sdw_dev(dev);
> > +	struct sdw_driver *drv = drv_to_sdw_driver(ddrv);
> > +
> > +	return !!sdw_get_device_id(slave, drv);
> > +}
> > +
> > +int sdw_slave_modalias(struct sdw_slave *slave, char *buf, size_t size)
> 
> I'd put const to slave argument, as it won't be modified.

right...

> 
> > --- a/include/linux/mod_devicetable.h
> > +++ b/include/linux/mod_devicetable.h
> > @@ -228,6 +228,13 @@ struct hda_device_id {
> >  	unsigned long driver_data;
> >  };
> >  
> > +struct sdw_device_id {
> > +	__u16 mfg_id;
> > +	__u16 part_id;
> > +	__u8 class_id;
> > +	kernel_ulong_t driver_data;
> 
> Better to think of alignment.

sorry not quite clear, do you mind elaborating which ones to align?

> 
> 
> > --- /dev/null
> > +++ b/include/linux/soundwire/sdw.h
> ....
> > +/**
> > + * struct sdw_bus: SoundWire bus
> > + *
> > + * @dev: Master linux device
> > + * @link_id: Link id number, can be 0 to N, unique for each Master
> > + * @slaves: list of Slaves on this bus
> > + * @assigned: logical addresses assigned, Index 0 (broadcast) would be unused
> > + * @bus_lock: bus lock
> > + */
> > +struct sdw_bus {
> > +	struct device *dev;
> > +	unsigned int link_id;
> > +	struct list_head slaves;
> > +	bool assigned[SDW_MAX_DEVICES + 1];
> 
> Why not a bitmap?

That a very good suggestion, it will help in other things too :)

-- 
~Vinod