Message-Id: <201209210931.03109.hverkuil@xs4all.nl>
Date:	Fri, 21 Sep 2012 09:31:03 +0200
From:	Hans Verkuil <hverkuil@...all.nl>
To:	"andrey.smirnov@...vergeddevices.net" 
	<andrey.smirnov@...vergeddevices.net>
Cc:	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] Add a core driver for SI476x MFD

On Fri September 21 2012 03:05:41 andrey.smirnov@...vergeddevices.net wrote:
> On 09/13/2012 11:44 PM, Hans Verkuil wrote:
> > Hi Andrey!
> >
> > Thanks for posting this driver. One request for the future: please split this
> > patch up in smaller pieces: one for each c source for example. That makes it
> > easier to review.
> 
> Will do for next version.
> 
> > +
> > +/**
> > + * __core_send_command() - sends a command to si476x and waits its
> > + * response
> > + * @core:    si476x_device structure for the device we are
> > + *            communicating with
> > + * @command:  command id
> > + * @args:     command arguments we are sending
> > + * @argn:     actual size of @args
> > + * @response: buffer to place the expected response from the device
> > + * @respn:    actual size of @response
> > + * @usecs:    amount of time to wait before reading the response (in
> > + *            usecs)
> > + *
> > + * Function returns 0 on succsess and negative error code on
> > + * failure
> > + */
> > +static int __core_send_command(struct si476x_core *core,
> > +				    const u8 command,
> > +				    const u8 args[],
> > +				    const int argn,
> > +				    u8 resp[],
> > +				    const int respn,
> > +				    const int usecs)
> > +{
> > +	struct i2c_client *client = core->client;
> > +	int err;
> > +	u8  data[CMD_MAX_ARGS_COUNT + 1];
> > +
> > +	if (argn > CMD_MAX_ARGS_COUNT) {
> > +		err = -ENOMEM;
> > +		goto exit;
> > Why goto exit? There is no clean up after the exit label, so just return
> > immediately. Ditto for all the other goto exit's in this function.
> 
> To have only just on point of exit from the function that's just
> personal coding style preference.
> There are no technical reasons behind that, I can change that.
> 
> >
> >> +	}
> >> +
> >> +	if (!client->adapter) {
> >> +		err = -ENODEV;
> >> +		goto exit;
> >> +	}
> >> +
> >> +	/* First send the command and its arguments */
> >> +	data[0] = command;
> >> +	memcpy(&data[1], args, argn);
> >> +	DBG_BUFFER(&client->dev, "Command:\n", data, argn + 1);
> >> +
> >> +	err = si476x_i2c_xfer(core, SI476X_I2C_SEND, (char *) data, argn + 1);
> >> +	if (err != argn + 1) {
> >> +		dev_err(&core->client->dev,
> >> +			"Error while sending command 0x%02x\n",
> >> +			command);
> >> +		err = (err >= 0) ? -EIO : err;
> >> +		goto exit;
> >> +	}
> >> +	/* Set CTS to zero only after the command is send to avoid
> >> +	 * possible racing conditions when working in polling mode */
> >> +	atomic_set(&core->cts, 0);
> >> +
> >> +	if (!wait_event_timeout(core->command,
> >> +				atomic_read(&core->cts),
> >> +				usecs_to_jiffies(usecs) + 1))
> >> +		dev_warn(&core->client->dev,
> >> +			 "(%s) [CMD 0x%02x] Device took too much time to answer.\n",
> >> +			 __func__, command);
> >> +
> >> +	/*
> >> +	  When working in polling mode, for some reason the tuner will
> >> +	  report CTS bit as being set in the first status byte read,
> >> +	  but all the consequtive ones will return zros until the
> >> +	  tuner is actually completed the POWER_UP command. To
> >> +	  workaround that we wait for second CTS to be reported
> >> +	 */
> >> +	if (unlikely(!core->client->irq && command == CMD_POWER_UP)) {
> >> +		if (!wait_event_timeout(core->command,
> >> +					atomic_read(&core->cts),
> >> +					usecs_to_jiffies(usecs) + 1))
> >> +			dev_warn(&core->client->dev,
> >> +				 "(%s) Power up took too much time.\n",
> >> +				 __func__);
> >> +	}
> >> +
> >> +	/* Then get the response */
> >> +	err = si476x_i2c_xfer(core, SI476X_I2C_RECV, resp, respn);
> >> +	if (err != respn) {
> >> +		dev_err(&core->client->dev,
> >> +			"Error while reading response for command 0x%02x\n",
> >> +			command);
> >> +		err = (err >= 0) ? -EIO : err;
> >> +		goto exit;
> >> +	}
> >> +	DBG_BUFFER(&client->dev, "Response:\n", resp, respn);
> >> +
> >> +	err = 0;
> >> +
> >> +	if (resp[0] & SI476X_ERR) {
> >> +		dev_err(&core->client->dev, "Chip set error flag\n");
> >> +		err = si476x_core_parse_and_nag_about_error(core);
> >> +		goto exit;
> >> +	}
> >> +
> >> +	if (!(resp[0] & SI476X_CTS))
> >> +		err = -EBUSY;
> >> +exit:
> >> +	return err;
> >> +}
> >> +
> >> +#define CORE_SEND_COMMAND(core, cmd, args, resp, timeout)		\
> >> +	__core_send_command(core, cmd, args,				\
> >> +			    ARRAY_SIZE(args),				\
> >> +			    resp, ARRAY_SIZE(resp),			\
> >> +			    timeout)
> >> +
> >> +
> >> +static int __cmd_tune_seek_freq(struct si476x_core *core,
> >> +				uint8_t cmd,
> >> +				const uint8_t args[], size_t argn,
> >> +				uint8_t *resp, size_t respn,
> >> +				int (*clear_stcint) (struct si476x_core *core))
> >> +{
> >> +	int err;
> >> +
> >> +	atomic_set(&core->stc, 0);
> >> +	err = __core_send_command(core, cmd, args, argn,
> >> +				  resp, respn,
> >> +				  atomic_read(&core->timeouts.command));
> >> +	if (!err) {
> > Invert the test to simplify indentation.
> >
> >> +		if (!wait_event_timeout(core->tuning,
> >> +		atomic_read(&core->stc),
> >> +		usecs_to_jiffies(atomic_read(&core->timeouts.tune)) + 1)) {
> > Weird indentation above. Indent the arguments more to the right.
> 
> 80 symbol line length limit is the reason for that indentation.

It's not a limit, it's a warning only. Usually readability improves if such
long lines are split up or otherwise shortened, but if readability becomes
worse because of that, then just leave in the long line.

> 
> >
> > Andrey, you should look at the drivers/media/radio/si4713-i2c.c source.
> > It is for the same chip family and is much, much smaller.
> >
> > See if you can use some of the code that's there.
> 
> I did when I started writing the driver, that driver and driver for
> wl1273 were my two examples. In my initial version of the driver I tried
> to blend both si4713 and si476x into one generic driver, but the problem
> is: si4713 is a transmitter and si476x are receiver chips, the
> "impedance mismatch" in functionality of the two, IMHO, was too much to
> justify the unification.

But the way the commands are handled, etc. should be the same or very similar.
That's the main area where I suspect you can reuse code from those other
drivers.

> Thanks for review, and I'll try to incorporate your suggestions into my
> next version of the patches.

Thanks!

Regards,

	Hans
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