2.6内核中被废弃的pci_present()

在pci驱动是使用pci_present()函数在init函数中，编译过程中报错。

其中的源码为：

static int __init shao_init(void) { int init_ret; if (!pci_present()){ printk("This kernel version does not support PCI.../n"); return -ENODEV; } if(!pci_register_driver(&shao_driver)){ pci_unregister_driver(&shao_driver); return -ENODEV; } else printk("----------pci_register_driver success----------/n");  

error原因是：

error: implicit declaration of function ‘pci_present’

后来查阅了一些资料，发现下文：

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Linux Kernel Mailing List wrote: 
> ChangeSet 1.1317, 2003/06/05 12:04:33-07:00, greg@kroah.com 
> 
> [PATCH] PCI: move pci_present() into drivers/pci/search.c 
> 
> This will let not have to export the pci_devices variable. 

pci_present() should be killed. It's left over from 2.0 or 1.2 days, 
and has no meaning anymore. 

The old-kernel use was to determine if a PCI bus. Drivers had to check 
if a PCI bus was present, before probing for a PCI device using the 
old-old find-by-slot-and-busid method of PCI bus probing. As the 
now-old method of PCI bus probing (pci_find_device) and the current PCI 
API both provide correct behavior when no PCI bus is present, 
pci_present() itself no longer has any meaning and is entirely redundant. 

At the very least, we should use the gcc "deprecated" attribute on 
pci_present definitions, both normal and no-op. 

IMO pci_present should go before 2.6.0... it's lived long enough. 

        Jeff 

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或许我可以理解为，pci驱动已经被2.6内核默认支持，不存在甄别支持不支持的问题，在boot阶段，linux内核已经将PCI设备总线初始化并分配好了。