linux-kernel - Re: [PATCH 02/06] MFD: DA9052/53 MFD core module v9 Added ADC support

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Message-ID: <20120109223725.GG30766@opensource.wolfsonmicro.com>
Date:	Mon, 9 Jan 2012 22:37:25 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Ashish Jangam <ashish.jangam@...tcummins.com>
Cc:	linux-kernel@...r.kernel.org, Dajun <dajun.chen@...semi.com>,
	arnd@...db.de, sameo@...ux.intel.com,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Anton Vorontsov <avorontsov@...mvista.com>
Subject: Re: [PATCH 02/06] MFD: DA9052/53 MFD core module v9 Added ADC
	support

On Mon, Jan 09, 2012 at 02:16:10PM +0530, Ashish Jangam wrote:
> Re-submitting the patch.

This is patch 2/6 - where are patches 1 and 3-6?

> +	/* Channel gets activated on enabling the Conversion bit */
> +	mux_sel = chan_mux[channel] | DA9052_ADC_MAN_MAN_CONV;
> +
> +	if (da9052->auxadc_active) {
> +		ret = -EBUSY;
> +		goto err;
> +	}
> +
> +	/* Enqueue the request */
> +	list_add(&req->list, &da9052->auxadc_pending);

Maintaining a list of outstanding requests seems a bit odd if it's only
possible to have a single active request at any one time.

> +
> +	ret = da9052_reg_write(da9052, DA9052_ADC_MAN_REG, mux_sel);
> +	if (ret < 0)
> +		goto err;
> +
> +	da9052->auxadc_active = channel;
> +
> +	mutex_unlock(&da9052->auxadc_lock);
> +
> +	/* Wait for an interrupt */
> +	wait_for_completion_timeout(&req->done, msecs_to_jiffies(500));
> +
> +	mutex_lock(&da9052->auxadc_lock);

With only one request being possible at once just not dropping the mutex
seems like the easiest approach - it'll mean that userspace doesn't need
to worry about -EBUSY and you could save all the allocation, deallocation
and list management.  As things stand I expect userspace will run into
errors sometimes.
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