Re: [PATCH] PCI: Annotate pci_cache_line_size variables as __ro_after_init

[Heiner Kallweit <hkallweit1@gmail.com>]

On 17.04.2024 17:50, Bjorn Helgaas wrote:
> On Sat, Apr 13, 2024 at 11:05:52PM +0200, Heiner Kallweit wrote:
>> Annotate both variables as __ro_after_init, enforcing that they can't
>> be changed after the init phase.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>> ---
>>  drivers/pci/pci.c   | 4 ++--
>>  include/linux/pci.h | 4 ++--
>>  2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 5f8edba78..e7ac4474b 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -142,8 +142,8 @@ enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_DEFAULT;
>>   * the dfl or actual value as it sees fit.  Don't forget this is
>>   * measured in 32-bit words, not bytes.
>>   */
>> -u8 pci_dfl_cache_line_size = L1_CACHE_BYTES >> 2;
>> -u8 pci_cache_line_size;
>> +u8 pci_dfl_cache_line_size __ro_after_init = L1_CACHE_BYTES >> 2;
>> +u8 pci_cache_line_size __ro_after_init;
>>  
>>  /*
>>   * If we set up a device for bus mastering, we need to check the latency
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 69b10f2fb..cf63be0c9 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -2334,8 +2334,8 @@ extern int pci_pci_problems;
>>  
>>  extern unsigned long pci_cardbus_io_size;
>>  extern unsigned long pci_cardbus_mem_size;
>> -extern u8 pci_dfl_cache_line_size;
>> -extern u8 pci_cache_line_size;
>> +extern u8 pci_dfl_cache_line_size __ro_after_init;
>> +extern u8 pci_cache_line_size __ro_after_init;
> 
> Is __ro_after_init required on the declaration, too?  I see a few uses
> in .h files, but not very many, and I would think it would be a linker
> thing that applies to the definition, where space is allocated.
> 
You're right, it's not needed on the declaration. I'll submit a v2.

>>  /* Architecture-specific versions may override these (weak) */
>>  void pcibios_disable_device(struct pci_dev *dev);
>> -- 
>> 2.44.0
>>