Re: [PATCH v2 1/2] igb_uio: compatible with upstream longterm kernel and RHEL6

[Jincheng Miao <jmiao-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 11/28/2014 01:01 AM, Thomas Monjalon wrote:
> 2014-10-31 15:37, Jincheng Miao:
>> Function pci_num_vf() is introduced from upstream linux-2.6.34. So
>> this patch make compatible with longterm kernel linux-2.6.32.63.
>>
>> For RHEL6's kernel, although it is based on linux-2.6.32, it has
>> pci_num_vf() implementation. As the same with commit 11ba0426,
>> pci_num_vf() is defined from RHEL6. So we should check the macro
>> RHEL_RELEASE_CODE to consider this situation.
> Please, could you explain in which case CONFIG_PCI_IOV is defined?
> The logic is a bit difficult to understand.

Yep, there is a little confusion for pci_num_vf():
1. it is available when CONFIG_PCI_IOV is defined.
2. it is introduced from upstream kernel v2.6.34 (fb8a0d9)
3. it is implemented from RHEL6.0, although the kernel version is 2.6.32.

The logic of this patch is:
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 34) && \
(!(defined(RHEL_RELEASE_CODE) && RHEL_RELEASE_CODE >= 
RHEL_RELEASE_VERSION(6, 0) && defined(CONFIG_PCI_IOV)))

Firstly it detects kernel version, if it is less than 2.6.34, and it is 
not RHEL-specified, then define pci_num_vf().

Secondly, it deals with RHEL-specified. If it is RHEL6.0 or later, and 
CONFIG_PCI_IOV is defined. we should not define pci_num_vf(). If any of 
these conditions is not reached, pci_num_vf() should be defined.


Some days ago, I setup dpdk for longterm kernel 2.6.32.63, and got error:
```
CC [M] 
/root/dpdk-source/build/build/lib/librte_eal/linuxapp/igb_uio/igb_uio.o
/root/dpdk-source/build/build/lib/librte_eal/linuxapp/igb_uio/igb_uio.c: 
In function ‘show_max_vfs’:
/root/dpdk-source/build/build/lib/librte_eal/linuxapp/igb_uio/igb_uio.c:75: 
error: implicit declaration of function ‘pci_num_vf’
```

This problem is introduced by commit 11ba04265

commit 11ba04265cfd2a53c12c030fcaa5dfe7eed39a42
Author: Guillaume Gaudonville <guillaume.gaudonville-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
Date: Wed Sep 3 10:18:23 2014 +0200

igb_uio: fix build on RHEL 6.3

- pci_num_vf() is already defined in RHEL 6
- pci_intx_mask_supported is already defined in RHEL 6.3
- pci_check_and_mask_intx is already defined in RHEL 6.3

Signed-off-by: Guillaume Gaudonville <guillaume.gaudonville-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
Signed-off-by: David Marchand <david.marchand-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>

+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 34) && \
+ !defined(CONFIG_PCI_IOV)

That is because longterm kernel 2.6.32.63 defined CONFIG_PCI_IOV, but it 
lacks pci_num_vf(),
after above processing, pci_num_vf() is still not existed, then build fail.

My patch could work around it, and can deal with RHEL-specified kernel.


>>   #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 34) && \
>> -	!defined(CONFIG_PCI_IOV)
>> +       (!(defined(RHEL_RELEASE_CODE) && \
>> +          RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(6, 0) && \
>> +          defined(CONFIG_PCI_IOV)))
>>   
>>   static int pci_num_vf(struct pci_dev *dev)
>>   {