linux-kernel - Re: [PATCH V2 2/3] dmaengine: qcom_hidma: add support for the new revision

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Date:   Fri, 10 Nov 2017 14:17:16 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Sinan Kaya <okaya@...eaurora.org>, dmaengine@...r.kernel.org,
        Timur Tabi <timur@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH V2 2/3] dmaengine: qcom_hidma: add support for the new
 revision



On 10/11/17 14:03, Sinan Kaya wrote:
> +linux-acpi, +Rafael for context
> 
> On 11/8/2017 12:51 PM, Robin Murphy wrote:
>> Apologies if I wasn't very clear, but what I meant to imply by dropping the of_device_get_match_data() hint was to follow one of the common patterns where you either just have some version token:
>>
>>      enum foo_ver {
>>          FOO_V1,
>>          ...
>>      }
>>
>>      struct acpi_device_id foo_acpi_ids[] = {
>>          { "_FOO0001", FOO_V1 },
>>          ...
>>      }
>>
>>      struct of_device_id foo_of_match[] = {
>>          { .compatible = "foo,v1", .data = (void *)FOO_V1 },
>>          ...
>>      }
>>
>>      int foo_probe(struct device *dev) {
>>          ...
>>          foodev->version = (enum foo_ver)
>>                  of_device_get_match_data(&dev->of_node)
>>          ...
>>      }
>>
>>      int foo_reset(struct foodev *foodev) {
>>          if (foodev->version == FOO_V1)
>>              writel(0, foodev->base + 0x20);
>>          else
>>              writel(0, foodev->base + 0x30);
>>      }
> 
> I did post v3 with this approach. However, I could not really find a ACPI function that
> returns the driver data very similar to of_device_get_match_data(). The only thing
> that is closer is acpi_match_device().

Yeah, I left the "follow the status quo and open-code it" part out of 
the above example for brevity ;)

Probably 95% of the calls to acpi_match_device() are only doing so to 
retrieve the driver_data, so the helper could provide scope for further 
cleanup if anyone wants, too.

> I introduced this new function as part of the v3 series.
> 
> Let me know if I'm missing something.
v3 looks good, thanks for persevering - I'll leave the rest up to Vinod 
and Rafael.

Cheers,
Robin.