linux-kernel - Re: [PATCH v8 6/7] iio: accel: kionix-kx022a: Add a function to retrieve number of bytes in buffer

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Message-ID: <eb47d0c9-9144-c947-f91e-d487c6ec9c45@gmail.com>
Date:   Thu, 24 Aug 2023 15:52:56 +0300
From:   Matti Vaittinen <mazziesaccount@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mehdi Djait <mehdi.djait.k@...il.com>
Cc:     jic23@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        robh+dt@...nel.org, lars@...afoo.de, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v8 6/7] iio: accel: kionix-kx022a: Add a function to
 retrieve number of bytes in buffer

On 8/24/23 14:58, Andy Shevchenko wrote:
> On Wed, Aug 23, 2023 at 11:16:40PM +0200, Mehdi Djait wrote:
>> Since Kionix accelerometers use various numbers of bits to report data, a
>> device-specific function is required.
>> Implement the function as a callback in the device-specific chip_info structure
> 
> ...
> 
>> +	int ret, fifo_bytes;
>> +
>> +	ret = regmap_read(data->regmap, KX022A_REG_BUF_STATUS_1, &fifo_bytes);
>> +	if (ret) {
>> +		dev_err(data->dev, "Error reading buffer status\n");
>> +		return ret;
>> +	}
>> +
>> +	if (fifo_bytes == KX022A_FIFO_FULL_VALUE)
>> +		return KX022A_FIFO_MAX_BYTES;
>> +
>> +	return fifo_bytes;
> 
> This will be called each time ->get_fifo_bytes() called.
> Do you expect the fifo_bytes to be changed over times?
> Shouldn't we simply cache the value?

I think this value tells how many samples there currently is in the 
FIFO. Caching it does not sound meaningful unless I am missing something.

Yours,
	-- Matti

-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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