linux-kernel - Re: [PATCH v3 07/15] media: i2c: ds90ub960: Add support for I2C_RX

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Message-ID: <a852a4d2-a367-4900-a6f0-a10f23549d0e@ideasonboard.com>
Date: Thu, 5 Dec 2024 16:02:26 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Jai Luthra <jai.luthra@...asonboard.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Hans Verkuil <hverkuil-cisco@...all.nl>, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 07/15] media: i2c: ds90ub960: Add support for I2C_RX_ID

Hi,

On 05/12/2024 14:00, Jai Luthra wrote:
> Hi Tomi,
> 
> On Dec 05, 2024 at 10:31:42 +0200, Andy Shevchenko wrote:
>> On Wed, Dec 04, 2024 at 01:05:21PM +0200, Tomi Valkeinen wrote:
>>> Normally the driver accesses both the RX and the TX port registers via a
>>> paging mechanism: one register is used to select the page (i.e. the
>>> port), which dictates the port used when accessing the port specific
>>> registers.
>>>
>>> The downside to this is that while debugging it's almost impossible to
>>> access the port specific registers from the userspace, as the driver can
>>> change the page at any moment.
>>>
>>> The hardware supports another access mechanism: using the I2C_RX_ID
>>> registers (one for each RX port), i2c addresses can be chosen which,
>>> when accessed, will always use the specific port's registers, skipping
>>> the paging mechanism.
>>>
>>> The support is only for the RX port, but it has proven very handy while
>>> debugging and testing. So let's add the code for this, but hide it
>>> behind a disabled define.
>>
>> ...
>>
>>>   #define MHZ(v) ((u32)((v) * 1000000U))
>>
>> Missed HZ_PER_MHZ from previous patch?
>>
>> ...
>>
>>> +#ifdef UB960_DEBUG_I2C_RX_ID
>>> +	for (unsigned int i = 0; i < 4; i++)
>>
>> Should it use _MAX_RX_NPORTS instead of 4?
>>
> 
> Instead of hardcoded value or the macro, it is better to use
> priv->hw_data->num_rxports.
> 
> The cut-down variant of this deser only has 2 ports for example.
> https://www.ti.com/lit/gpn/ds90ub954-q1

Yes, that's true. I'll use the hw_data.

  Tomi