linux-kernel - Re: [PATCH net-next v6 8/8] mfd: zl3073x: Register DPLL sub-device during init

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Message-ID: <ef8ae196-84c9-447e-98ff-071d347531d5@redhat.com>
Date: Wed, 7 May 2025 14:36:21 +0200
From: Ivan Vecera <ivecera@...hat.com>
To: Lee Jones <lee@...nel.org>
Cc: netdev@...r.kernel.org, Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
 Jiri Pirko <jiri@...nulli.us>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Prathosh Satish <Prathosh.Satish@...rochip.com>,
 "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 Andy Shevchenko <andy@...nel.org>, Michal Schmidt <mschmidt@...hat.com>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org
Subject: Re: [PATCH net-next v6 8/8] mfd: zl3073x: Register DPLL sub-device
 during init

On 07. 05. 25 1:06 odp., Lee Jones wrote:
> On Fri, 02 May 2025, Ivan Vecera wrote:
> 
>>
>>
>> On 01. 05. 25 3:22 odp., Lee Jones wrote:
>>> On Wed, 30 Apr 2025, Ivan Vecera wrote:
>>>
>>>> Register DPLL sub-devices to expose the functionality provided
>>>> by ZL3073x chip family. Each sub-device represents one of
>>>> the available DPLL channels.
>>>>
>>>> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
>>>> ---
>>>> v4->v6:
>>>> * no change
>>>> v3->v4:
>>>> * use static mfd cells
>>>> ---
>>>>    drivers/mfd/zl3073x-core.c | 19 +++++++++++++++++++
>>>>    1 file changed, 19 insertions(+)
>>>>
>>>> diff --git a/drivers/mfd/zl3073x-core.c b/drivers/mfd/zl3073x-core.c
>>>> index 050dc57c90c3..3e665cdf228f 100644
>>>> --- a/drivers/mfd/zl3073x-core.c
>>>> +++ b/drivers/mfd/zl3073x-core.c
>>>> @@ -7,6 +7,7 @@
>>>>    #include <linux/device.h>
>>>>    #include <linux/export.h>
>>>>    #include <linux/math64.h>
>>>> +#include <linux/mfd/core.h>
>>>>    #include <linux/mfd/zl3073x.h>
>>>>    #include <linux/module.h>
>>>>    #include <linux/netlink.h>
>>>> @@ -755,6 +756,14 @@ static void zl3073x_devlink_unregister(void *ptr)
>>>>    	devlink_unregister(ptr);
>>>>    }
>>>> +static const struct mfd_cell zl3073x_dpll_cells[] = {
>>>> +	MFD_CELL_BASIC("zl3073x-dpll", NULL, NULL, 0, 0),
>>>> +	MFD_CELL_BASIC("zl3073x-dpll", NULL, NULL, 0, 1),
>>>> +	MFD_CELL_BASIC("zl3073x-dpll", NULL, NULL, 0, 2),
>>>> +	MFD_CELL_BASIC("zl3073x-dpll", NULL, NULL, 0, 3),
>>>> +	MFD_CELL_BASIC("zl3073x-dpll", NULL, NULL, 0, 4),
>>>> +};
>>>
>>> What other devices / subsystems will be involved when this is finished?
>>
>> Lee, btw. I noticed from another discussion that you mentioned that
>> mfd_cell->id should not be used outside MFD.
>>
>> My sub-drivers uses this to get DPLL channel number that should be used
>> for the particular sub-device.
>>
>> E.g.
>> 1) MFD_CELL_BASIC("zl3073x-dpll", NULL, NULL, 0, 2);
>> 2) MFD_CELL_BASIC("zl3073x-phc", NULL, NULL, 0, 3);
>>
>> In these cases dpll_zl3073x sub-driver will use DPLL channel 2 for this
>> DPLL sub-device and ptp_zl3073x sub-driver will use DPLL channel 3 for
>> this PHC sub-device.
>>
>> platform_device->id cannot be used for this purpose in conjunction with
>> PLATFORM_DEVID_AUTO as that ->id can be arbitrary.
>>
>> So if I cannot use mfd_cell->id what should I use for that case?
>> Platform data per cell with e.g. the DPLL channel number?
> 
> Yes, using the device ID for anything other than enumeration is a hack.
> 
> Channel numbers and the like should be passed as platform data.

OK, I will send v7 quickly.

Ivan