Re: [PATCH] PCI/PTM: Build debugfs code only if CONFIG_DEBUG_FS is enabled

[Eric Biggers <ebiggers@kernel.org>]

On Sun, Jun 08, 2025 at 09:03:05AM +0530, Manivannan Sadhasivam wrote:
> Otherwise, the following build error will happen for CONFIG_DEBUG_FS=n &&
> CONFIG_PCIE_PTM=y.
> 
>     drivers/pci/pcie/ptm.c:498:25: error: redefinition of 'pcie_ptm_create_debugfs'
>       498 | struct pci_ptm_debugfs *pcie_ptm_create_debugfs(struct device *dev, void *pdata,
>           |                         ^
>     ./include/linux/pci.h:1915:2: note: previous definition is here
>      1915 | *pcie_ptm_create_debugfs(struct device *dev, void *pdata,
>           |  ^
>     drivers/pci/pcie/ptm.c:546:6: error: redefinition of 'pcie_ptm_destroy_debugfs'
>       546 | void pcie_ptm_destroy_debugfs(struct pci_ptm_debugfs *ptm_debugfs)
>           |      ^
>     ./include/linux/pci.h:1918:1: note: previous definition is here
>      1918 | pcie_ptm_destroy_debugfs(struct pci_ptm_debugfs *ptm_debugfs) { }
>           |
> 
> Fixes: 132833405e61 ("PCI: Add debugfs support for exposing PTM context")
> Reported-by: Eric Biggers <ebiggers@kernel.org>
> Closes: https://lore.kernel.org/linux-pci/20250607025506.GA16607@sol
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
>  drivers/pci/pcie/ptm.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
> index ee5f615a9023..4bd73f038ffb 100644
> --- a/drivers/pci/pcie/ptm.c
> +++ b/drivers/pci/pcie/ptm.c
> @@ -254,6 +254,7 @@ bool pcie_ptm_enabled(struct pci_dev *dev)
>  }
>  EXPORT_SYMBOL(pcie_ptm_enabled);
>  
> +#if IS_ENABLED(CONFIG_DEBUG_FS)
>  static ssize_t context_update_write(struct file *file, const char __user *ubuf,
>  			     size_t count, loff_t *ppos)
>  {
> @@ -552,3 +553,4 @@ void pcie_ptm_destroy_debugfs(struct pci_ptm_debugfs *ptm_debugfs)
>  	debugfs_remove_recursive(ptm_debugfs->debugfs);
>  }
>  EXPORT_SYMBOL_GPL(pcie_ptm_destroy_debugfs);
> +#endif

Tested-by: Eric Biggers <ebiggers@kernel.org>

DEBUG_FS is a bool, not a tristate.  It would be more conventional to write
'#ifdef CONFIG_DEBUG_FS' instead of '#if IS_ENABLED(CONFIG_DEBUG_FS)'.

Also, the #if guards 300 lines of code.  Perhaps they belong in a separate .c
file?

- Eric