linux-kernel - Re: [PATCH v1] i2c: i2c-core-base: Modify the maximum idr id for i2c adapter

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Date:   Tue, 10 Jan 2023 16:39:47 +0800
From:   Riwen Lu <luriwen@...mail.com>
To:     Wolfram Sang <wsa@...nel.org>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, xiongxin@...inos.cn,
        Riwen Lu <luriwen@...inos.cn>
Subject: Re: [PATCH v1] i2c: i2c-core-base: Modify the maximum idr id for i2c
 adapter

在 2023/1/9 23:13, Wolfram Sang 写道:
> On Fri, Dec 16, 2022 at 10:07:51AM +0800, Riwen Lu wrote:
>> From: Riwen Lu <luriwen@...inos.cn>
>>
>> Change the maximum idr ID to INT_MAX for i2c adapter.
>> This fix the following adding i2c adapter error while the idr with
>> adap->nr has been allocated by other i2c driver, and find a proper ID
> 
> How did this happen that another i2c driver could get this? Were you
> able to follow the code paths that lead to this situation?
> 
Yes, it's happened in Phytium(Arm64) platform with MWV207 GPU.

1. The MWV207 GPU driver has registered I2C adapter, and allocated idr 
id 0-6 with i2c_adapter_idr.

# cd  /sys/class/i2c-adapter/i2c-0/
# ls
i2c-0  i2c-1  i2c-2  i2c-3  i2c-4  i2c-5  i2c-6
# cd i2c-0/
# ls
delete_device  device  i2c-dev  name  new_device  power  subsystem  uevent
# cat name
MWV207_I2C_0

2. The BIOS's ACPI DSDT has declared I2C device with _UID 0 as following:

         Device (I2C0)
         {
             Name (_HID, "PHYT0038")  // _HID: Hardware ID
             Name (_UID, Zero)  // _UID: Unique ID
             Name (_CRS, ResourceTemplate ()
             {
                 Memory32Fixed (ReadWrite,
                     0x28014000,
                     0x00001000,
                     )
                 Interrupt (ResourceConsumer, Level, ActiveHigh, 
Exclusive, ,, )
                 {
                     0x0000007C,
                 }
             })

             ...
         }

The Phytium i2c driver would register the i2c adapter with idr id 0 by 
calling function i2c_add_numbered_adapter(adap). Then, function 
idr_alloc(&i2c_adapter_idr, adap, adap->nr, adap->nr + 1, GFP_KERNEL)； 
allocate the idr failed because idr id adap->nr(It equal to _UID) has 
been allocated by MWV207 GPU, and print the following error:

couldn't get idr
i2c-phytium-platform PHYT0038:00: fail to add adapter: -16

This patch can solve the problem.
>> for it.
>> [  357.620685][ 3] [ T3655] ------------[ cut here ]------------
>> [  357.626544][ 3] [ T3655] couldn't get idr
>>
>> Signed-off-by: Riwen Lu <luriwen@...inos.cn>
>> ---
>>   drivers/i2c/i2c-core-base.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
>> index 7539b0740351..c2982861057a 100644
>> --- a/drivers/i2c/i2c-core-base.c
>> +++ b/drivers/i2c/i2c-core-base.c
>> @@ -1535,11 +1535,12 @@ static int __i2c_add_numbered_adapter(struct i2c_adapter *adap)
>>   	int id;
>>   
>>   	mutex_lock(&core_lock);
>> -	id = idr_alloc(&i2c_adapter_idr, adap, adap->nr, adap->nr + 1, GFP_KERNEL);
>> +	id = idr_alloc(&i2c_adapter_idr, adap, adap->nr, 0, GFP_KERNEL);
>>   	mutex_unlock(&core_lock);
>>   	if (WARN(id < 0, "couldn't get idr"))
>>   		return id == -ENOSPC ? -EBUSY : id;
>>   
>> +	adap->nr = id;
>>   	return i2c_register_adapter(adap);
>>   }
>>   
>> -- 
>> 2.25.1
>>