linux-kernel - Re: [PATCH 3/6] misc: sbrmi: Use regmap subsystem

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Message-ID: <1be9ef16-46f9-1312-2a61-4d0038e2d32f@amd.com>
Date: Thu, 4 Jul 2024 19:56:34 +0530
From: "Gupta, Akshay" <Akshay.Gupta@....com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux@...ck-us.net, arnd@...db.de, naveenkrishna.chatradhi@....com
Subject: Re: [PATCH 3/6] misc: sbrmi: Use regmap subsystem


On 7/4/2024 5:23 PM, Greg KH wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>
>
> On Thu, Jul 04, 2024 at 11:16:21AM +0000, Akshay Gupta wrote:
>> - regmap subsystem provides multiple benefits over direct smbus APIs
> In what way, please document.
Answered below.
>
>> - The susbsytem can be helpful in following cases
>>    - Differnet types of bus (i2c/i3c)
>>    - Different Register address size (1byte/2byte)
> Is that what is happening here?  I don't see i3c support...

This is a preparation for

1. I3C support: planning to add support, on AMD platforms BMC can 
communicate with SBRMI over I2C/I3C

2. patch 6/6 in patch series, is adding support for 2 bytes SBRMI 
register address size

>> --- a/include/misc/amd-sb.h
>> +++ b/include/misc/amd-sb.h
>> @@ -7,8 +7,8 @@
>>   #define _AMD_SB_H_
>>
>>   #include <linux/mutex.h>
>> -#include <linux/i2c.h>
> Why remove this?
In this patch "struct i2c_client" is removed, so no need for the header 
inclusion.
>
>>   #include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>>   /*
>>    * SB-RMI supports soft mailbox service request to MP1 (power management
>>    * firmware) through SBRMI inbound/outbound message registers.
>> @@ -23,11 +23,11 @@ enum sbrmi_msg_id {
>>
>>   /* Each client has this additional data */
>>   struct sbrmi_data {
>> -     struct i2c_client *client;
>> +     struct regmap *regmap;
>>        struct mutex lock;
>>        struct platform_device *pdev;
>>        u32 pwr_limit_max;
>> -};
>> +} __packed;
> Why is this suddenly required to be __packed?
>
> Isn't that going to cause more problems than it is worth?  And why is it
> worth it at all?
I will look into this and update.
>
> thanks,
>
> greg k-h