[alsa-devel] [PATCH v5 03/14] ASoC: SOF: Add driver debug support.

[Pierre-Louis Bossart]

On 3/29/19 12:04 PM, Takashi Iwai wrote:
> On Thu, 21 Mar 2019 17:10:05 +0100,
> Pierre-Louis Bossart wrote:
>>
>> +static ssize_t sof_dfsentry_read(struct file *file, char __user *buffer,
>> +				 size_t count, loff_t *ppos)
>> +{
>> +	struct snd_sof_dfsentry *dfse = file->private_data;
>> +	struct snd_sof_dev *sdev = dfse->sdev;
>> +	int size;
>> +	u32 *buf;
>> +	loff_t pos = *ppos;
>> +	size_t size_ret;
>> +
>> +	size = dfse->size;
>> +
>> +	/* validate position & count */
>> +	if (pos < 0)
>> +		return -EINVAL;
>> +	if (pos >= size || !count)
>> +		return 0;
>> +	/* find the minimum. min() is not used since it adds sparse warnings */
>> +	if (count > size - pos)
>> +		count = size - pos;
>> +
>> +	/* intermediate buffer size must be u32 multiple */
>> +	size = ALIGN(count, 4);
> 
> Doesn't pos need to be aligned to 32bit as well (at least at actually
> reading from iomem)?

Good point,  we can either return an error if the count in both a 
multiple of 32 bits, or do some caching to allow for arbitrary size 
access. The former is very simple but not sure if this is accepted 
behavior for debugfs.