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Subject: Re: [PATCH v3] hwmon/pmbus: use simple i2c probe function
To:     Stephen Kitt <steve@sk2.org>
Cc:     Jean Delvare <jdelvare@suse.com>, linux-hwmon@vger.kernel.org,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        Wolfram Sang <wsa@kernel.org>
References: <20200807173231.GA47449@roeck-us.net>
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From:   Guenter Roeck <linux@roeck-us.net>
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Message-ID: <383af0fb-7eb9-dea8-291c-962c6b9eedd1@roeck-us.net>
Date:   Sat, 8 Aug 2020 06:46:15 -0700
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On 8/7/20 11:53 PM, Stephen Kitt wrote:
> On Fri, 7 Aug 2020 21:07:07 +0200, Stephen Kitt <steve@sk2.org> wrote:
>=20
>> On Fri, 7 Aug 2020 10:32:31 -0700, Guenter Roeck <linux@roeck-us.net> =
wrote:
>>> On Fri, Aug 07, 2020 at 06:28:01PM +0200, Stephen Kitt wrote: =20
>>>> =20
>>>> -static int ltc2978_probe(struct i2c_client *client,
>>>> -			 const struct i2c_device_id *id)
>>>> +static int ltc2978_probe(struct i2c_client *client)
>>>>  {
>>>>  	int i, chip_id;
>>>>  	struct ltc2978_data *data;
>>>> @@ -670,10 +669,10 @@ static int ltc2978_probe(struct i2c_client
>>>> *client, return chip_id;
>>>> =20
>>>>  	data->id =3D chip_id;
>>>> -	if (data->id !=3D id->driver_data)
>>>> +	if (strcmp(client->name, ltc2978_id[data->id].name) !=3D 0)   =20
>>>
>>> I was about to apply this patch, but this is problematic: It assumes =
that
>>> __stringify(id) =3D=3D ltc2978_id[id].name and that ltc2978_id[id].dr=
iver_data
>>> =3D=3D id. While that is curently the case (as far as I can see), it =
is still
>>> unsafe. I think it would be much safer to use i2c_match_id() here. =20
>>
>> I=E2=80=99m not following the __stringify assumption
> [...]
>=20
> I get it, the code assumes there=E2=80=99s a bijection between the set =
of names and
> the set of driver_data values. So effectively we can=E2=80=99t log the =
detected name
> based on the chip_id...

Exactly.

Thanks,
Guenter


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