linux-kernel - Re: [PATCH] mfd: qcom-spmi-pmic: Add support for more chips versions

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Date:	Fri, 07 Nov 2014 17:08:10 -0700
From:	Gilad Avidov <gavidov@...eaurora.org>
To:	"Ivan T. Ivanov" <iivanov@...sol.com>,
	Bjorn Andersson <bjorn@...o.se>
CC:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Stanimir Varbanov <svarbanov@...sol.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH] mfd: qcom-spmi-pmic: Add support for more chips versions

On 11/6/2014 12:54 AM, Ivan T. Ivanov wrote:
> On Wed, 2014-11-05 at 17:36 -0800, Bjorn Andersson wrote:
>> On Wed, Nov 5, 2014 at 10:31 AM, Ivan T. Ivanov <iivanov@...sol.com> wrote:
>>> On Wed, 2014-11-05 at 10:11 -0800, Bjorn Andersson wrote:
>>>> On Tue, Nov 4, 2014 at 5:33 AM, Ivan T. Ivanov <iivanov@...sol.com>
>>>> wrote:
>>>> [..]
>>>>> @@ -28,11 +144,27 @@ static int pmic_spmi_probe(struct spmi_device
>>>>> *sdev)
>>>>>   {
>>>>>          struct device_node *root = sdev->dev.of_node;
>>>>>          struct regmap *regmap;
>>>>> +       struct property *prop;
>>>>> +       int major, minor, ret;
>>>>> +       char *name, compatible[32];
>>>>>
>>>>>          regmap = devm_regmap_init_spmi_ext(sdev,
>>>>> &spmi_regmap_config);
Hi Ivan, I have a general question about this driver/layer.
Since the driver is using regmap, why does it need to be 
qcom-*spmi*-pmic ? could we drop the spmi part?
regmap's point is abstraction of  the bus technology, and indeed some 
PMICs use i2c.

>>>>>          if (IS_ERR(regmap))
>>>>>                  return PTR_ERR(regmap);
>>>>>
>>>>> +       ret = pmic_spmi_read_revid(regmap, &name, &major, &minor);
>>>>> +       if (!ret) {
>>>>> +               snprintf(compatible, ARRAY_SIZE(compatible),
>>>>> "qcom,%s-v%d.%d",
>>>>> +                        name, major, minor);
>>>>> +               prop = kzalloc(sizeof(*prop), GFP_KERNEL);
>>>>> +               if (prop) {
>>>>> +                       prop->name = kstrdup("compatible",
>>>>> GFP_KERNEL);
>>>>> +                       prop->value = kstrdup(compatible,
>>>>> GFP_KERNEL);
>>>>> +                       prop->length = strlen(prop->value);
>>>>> +                       of_update_property(root, prop);
>>>>> +               }
>>>>> +       }
>>>>> +
>>>> Why would you do this?
>>>> What benefit does it give to patch the of_node to have a more
>>>> specific
>>>> compatible?
>>> Some of the child device drivers have to know PMIC chip revision.
>>>
>> So your plan is to have a strstr(parent->compatible, "-v2") there?
> Actually also PMIC subtype (pm8841, pm8226...) is also required, so
> the plan is to have something like this:
>
> {
>          static const struct of_device_id pmic_match_table[] = {
>                  { .compatible = "qcom,pm8941-v1.0" },
>                  { .compatible = "qcom,pm8841-v0.0" },
>                  { }
>
>          };
>
>          const struct of_device_id *match;
>
>          match = of_match_device(pmic_match_table, pdev->dev.parent);
>          if (match) {
>                  dev_info(&pdev->dev, "%s chip detected\n", match->compatible);
>          }
> }
>
>> Could you be a little bit more elaborate on what you're trying to do
>> and which child devices that might be?
> For example ADC drivers are required temperature compensation based
> on PMIC variant and chip manufacturer.
>
> This patch have one issue, at least :-). Using of_update_property will prevent
> driver to be build as module. which, I think, is coming from the fact the
> on first load it will modify device compatible property and will be impossible
> driver to match device id again. Still thinking how to overcome this.
>
> Regards,
> Ivan
> --
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-- 
Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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