linux-kernel - Re: [PATCH 2/2] net, thunder, bgx: Add support for ACPI binding.

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Message-ID: <55C4A7AC.1080902@linaro.org>
Date:	Fri, 07 Aug 2015 14:42:20 +0200
From:	Tomasz Nowicki <tomasz.nowicki@...aro.org>
To:	Robert Richter <robert.richter@...iumnetworks.com>
CC:	David Daney <ddaney.cavm@...il.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	linux-mips@...ux-mips.org, Sunil Goutham <sgoutham@...ium.com>,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 2/2] net, thunder, bgx: Add support for ACPI binding.

On 07.08.2015 13:56, Robert Richter wrote:
> On 07.08.15 12:52:41, Tomasz Nowicki wrote:
>> On 07.08.2015 12:43, Robert Richter wrote:
>>> On 07.08.15 10:09:04, Tomasz Nowicki wrote:
>>>> On 07.08.2015 02:33, David Daney wrote:
>>>
>>> ...
>>>
>>>>> +#else
>>>>> +
>>>>> +static int bgx_init_acpi_phy(struct bgx *bgx)
>>>>> +{
>>>>> +	return -ENODEV;
>>>>> +}
>>>>> +
>>>>> +#endif /* CONFIG_ACPI */
>>>>> +
>>>>>   #if IS_ENABLED(CONFIG_OF_MDIO)
>>>>>
>>>>>   static int bgx_init_of_phy(struct bgx *bgx)
>>>>> @@ -882,7 +1010,12 @@ static int bgx_init_of_phy(struct bgx *bgx)
>>>>>
>>>>>   static int bgx_init_phy(struct bgx *bgx)
>>>>>   {
>>>>> -	return bgx_init_of_phy(bgx);
>>>>> +	int err = bgx_init_of_phy(bgx);
>>>>> +
>>>>> +	if (err != -ENODEV)
>>>>> +		return err;
>>>>> +
>>>>> +	return bgx_init_acpi_phy(bgx);
>>>>>   }
>>>>>
>>>>
>>>> If kernel can work with DT and ACPI (both compiled in), it should take only
>>>> one path instead of probing DT and ACPI sequentially. How about:
>>>>
>>>> @@ -902,10 +925,9 @@ static int bgx_probe(struct pci_dev *pdev, const struct
>>>> pci_device_id *ent)
>>>>   	bgx_vnic[bgx->bgx_id] = bgx;
>>>>   	bgx_get_qlm_mode(bgx);
>>>>
>>>> -	snprintf(bgx_sel, 5, "bgx%d", bgx->bgx_id);
>>>> -	np = of_find_node_by_name(NULL, bgx_sel);
>>>> -	if (np)
>>>> -		bgx_init_of(bgx, np);
>>>> +	err = acpi_disabled ? bgx_init_of_phy(bgx) : bgx_init_acpi_phy(bgx);
>>>> +	if (err)
>>>> +		goto err_enable;
>>>>
>>>>   	bgx_init_hw(bgx);
>>>
>>> I would not pollute bgx_probe() with acpi and dt specifics, and instead
>>> keep bgx_init_phy(). The typical design pattern for this is:
>>>
>>> static int bgx_init_phy(struct bgx *bgx)
>>> {
>>> #ifdef CONFIG_ACPI
>>>          if (!acpi_disabled)
>>>                  return bgx_init_acpi_phy(bgx);
>>> #endif
>>>          return bgx_init_of_phy(bgx);
>>> }
>>>
>>> This adds acpi runtime detection (acpi=no), does not call dt code in
>>> case of acpi, and saves the #else for bgx_init_acpi_phy().
>>>
>>
>> I am fine with keeping it in bgx_init_phy(), however we can drop there
>> #ifdefs since both of bgx_init_{acpi,of}_phy calls have empty stub for !ACPI
>> and !OF case. Like that:
>>
>> static int bgx_init_phy(struct bgx *bgx)
>> {
>>
>>          if (!acpi_disabled)
>>                  return bgx_init_acpi_phy(bgx);
>> 	else
>>          	return bgx_init_of_phy(bgx);
>> }
>
> As said, keeping it in #ifdefs makes the empty stub function for !acpi
> obsolete, which makes the code smaller and better readable. This style
> is common practice in the kernel. Apart from that, the 'else' should
> be dropped as it is useless.
>

I would't say the code is better readable (bgx_init_of_phy has still two 
stubs) but this is just cosmetic, my point was to use run time detection 
using acpi_disabled.

Tomasz
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