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SubjectRe: [PATCH v2 3/3] gpio: pcf857x: Add OF support
On 08/25/2013 02:15 AM, Laurent Pinchart wrote:
> On Saturday 24 August 2013 16:13:11 Tomasz Figa wrote:
>> On Saturday 24 of August 2013 02:54:07 Laurent Pinchart wrote:
>>> On Saturday 24 August 2013 02:41:59 Tomasz Figa wrote:
>>>> On Tuesday 20 of August 2013 01:04:54 Laurent Pinchart wrote:
>>>>> Add DT bindings for the pcf857x-compatible chips and parse the
>>>>> device tree node in the driver.
>>>>>
>>>>> Signed-off-by: Laurent Pinchart
>>>>> <laurent.pinchart+renesas@ideasonboard.com> ---
>>>>>
>>>>> .../devicetree/bindings/gpio/gpio-pcf857x.txt | 71 +++++++++++++
>>>>> drivers/gpio/gpio-pcf857x.c | 57 ++++++++++---
>>>>> 2 files changed, 119 insertions(+), 9 deletions(-)
>>>>> create mode 100644
>
> [snip]
>
>>>>> diff --git a/drivers/gpio/gpio-pcf857x.c
>>>>> b/drivers/gpio/gpio-pcf857x.c
>>>>> index 070e81f..50a90f1 100644
>>>>> --- a/drivers/gpio/gpio-pcf857x.c
>>>>> +++ b/drivers/gpio/gpio-pcf857x.c
>>>
>>> [snip]
>>>
>>>>> @@ -50,6 +52,27 @@ static const struct i2c_device_id pcf857x_id[] =
>>>>> {
>>>>>
>>>>> };
>>>>> MODULE_DEVICE_TABLE(i2c, pcf857x_id);
>>>>>
>>>>> +#ifdef CONFIG_OF
>>>>> +static const struct of_device_id pcf857x_of_table[] = {
>>>>> + { .compatible = "nxp,pcf8574", .data = (void *)8 },
>>>>> + { .compatible = "nxp,pcf8574a", .data = (void *)8 },
>>>>> + { .compatible = "nxp,pca8574", .data = (void *)8 },
>>>>> + { .compatible = "nxp,pca9670", .data = (void *)8 },
>>>>> + { .compatible = "nxp,pca9672", .data = (void *)8 },
>>>>> + { .compatible = "nxp,pca9674", .data = (void *)8 },
>>>>> + { .compatible = "nxp,pcf8575", .data = (void *)16 },
>>>>> + { .compatible = "nxp,pca8575", .data = (void *)16 },
>>>>> + { .compatible = "nxp,pca9671", .data = (void *)16 },
>>>>> + { .compatible = "nxp,pca9673", .data = (void *)16 },
>>>>> + { .compatible = "nxp,pca9675", .data = (void *)16 },
>>>>> + { .compatible = "maxim,max7328", .data = (void *)8 },
>>>>> + { .compatible = "maxim,max7329", .data = (void *)8 },
>>>>> + { .compatible = "ti,tca9554", .data = (void *)8 },
>>>>> + { }
>>>>> +};
>>>>> +MODULE_DEVICE_TABLE(of, pcf857x_of_table);
>>>>> +#endif
>>>>> +
>>>>>
>>>>> /*
>>>>> * The pcf857x, pca857x, and pca967x chips only expose one read and
>>>>> * one write register. Writing a "one" bit (to match the reset
>>>>> @@ -257,14 +280,29 @@ fail:
>>>>> static int pcf857x_probe(struct i2c_client *client,
>>>>> const struct i2c_device_id *id)
>>>>> {
>>>>> - struct pcf857x_platform_data *pdata;
>>>>> + struct pcf857x_platform_data *pdata = client->dev.platform_data;
>>>>> + struct device_node *np = client->dev.of_node;
> > > > struct pcf857x *gpio;
>>>>> + unsigned int n_latch = 0;
>>>>> + unsigned int ngpio;
>>>>> int status;
>>>>>
>>>>> - pdata = client->dev.platform_data;
>>>>> - if (!pdata) {
>>>>> +#ifdef CONFIG_OF
>>>>> + if (np) {
>>>>
>>>> Wouldn't if (IS_ENABLED(CONFIG_OF)&& np) be sufficient here, without
>>>> the #ifdef? You would have to move the match table out of the #ifdef
>>>> in this case, though...
>>>
>>> That's the exact reason why I've used #ifdef CONFIG_OF here, I didn't
>>> want to add the overhead of the pcf857x_of_table when CONFIG_OF isn't
>>> defined.
>>
>> I'm not sure if I remember correctly, but I think there was something said
>> in one of discussions some time ago, that we should be moving away from
>> ifdef'ing such things, in favour of just having them compiled
>> unconditionally.
>
> There seems to be a general consensus to favor if (IS_ENABLED(CONFIG_OF))
> instead of #ifdef CONFIG_OF when possible. I'm not sure what the opinion is
> regarding using conditional compilation to avoid compiling unnecessary data
> tables in. I would vote for using it (there's no need to bloat the kernel
> unnecessarily on non-OF platforms), but I'll conform to whatever is decided to
> be best.
>
>> [Adding DT maintainers on Cc for more opinions.]
>
> I'll resubmit the patch with the DT bindings documentation fixed, and will
> submit yet another version if I need to remove the #ifdef.

I think it makes sense to keep this table compiled in conditionally,
size of
struct of_device_id is relatively large. While absolute increase in size
might not be that significant the relative increase is quite large -
appr. 130%.


Before $subject patch:

$ size drivers/gpio/gpio-pcf857x.o
text data bss dec hex filename
2228 140 0 2368 940 drivers/gpio/gpio-pcf857x.o

After applying the patch:

$ size drivers/gpio/gpio-pcf857x.o
text data bss dec hex filename
5284 140 0 5424 1530 drivers/gpio/gpio-pcf857x.o

--
Regards,
Sylwester


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