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SubjectRe: [PATCH 2/3] PCI: Define pr_fmt() and use pr_*() instead of printk()
Hi Mohan,

On Sat, Apr 20, 2019 at 07:05:30AM +0300, Mohan Kumar wrote:
> Define a pr_fmt() macro that convert all of the explicit printk() calls
> into corresponding pr_*().

I dropped the pr_fmt() parts of this because there's really no
benefit: we move the prefix from the actual printk() to the pr_fmt
definition, which is a little bit harder to understand for the reader,
and it makes the string harder to find, e.g., if you see "PCI: can't
add host bridge window" in the dmesg log and search for it in the
kernel source, you'll no longer find it.

I think pr_fmt does make sense if the prefix is used many times, but
for these cases, where it's only used once or twice, it doesn't seem
worthwhile.

> Signed-off-by: Mohan Kumar <mohankumar718@gmail.com>
> ---
> drivers/pci/bus.c | 5 ++++-
> drivers/pci/pci-stub.c | 11 +++++------
> drivers/pci/pci-sysfs.c | 3 ++-
> drivers/pci/pci.c | 5 +++--
> drivers/pci/quirks.c | 9 +++++----
> drivers/pci/setup-bus.c | 5 +++--
> drivers/pci/slot.c | 4 +++-
> 7 files changed, 25 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 5cb40b2..a742ef5 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -6,6 +6,9 @@
> * David Miller (davem@redhat.com)
> * Ivan Kokshaysky (ink@jurassic.park.msu.ru)
> */
> +
> +#define pr_fmt(fmt) "PCI: " fmt
> +
> #include <linux/module.h>
> #include <linux/kernel.h>
> #include <linux/pci.h>
> @@ -23,7 +26,7 @@ void pci_add_resource_offset(struct list_head *resources, struct resource *res,
>
> entry = resource_list_create_entry(res, 0);
> if (!entry) {
> - printk(KERN_ERR "PCI: can't add host bridge window %pR\n", res);
> + pr_err("can't add host bridge window %pR\n", res);

This is an example of doing two changes at once:

1) Converting "printk(KERN_ERR)" to "pr_err()"
2) Factoring out the "PCI: " prefix with pr_fmt()

The first change is worthwhile and I pulled that out and squashed it
into your first patch.

This patch (if we were going to do it) should contain *only* the
pr_fmt() factoring. So the first patch would look like this:

- printk(KERN_ERR "PCI: can't add host bridge window %pR\n", res);
+ pr_err("PCI: can't add host bridge window %pR\n", res);

and the second patch would look like this:

+#define pr_fmt(fmt) "PCI: " fmt
- pr_err("PCI: can't add host bridge window %pR\n", res);
+ pr_err("can't add host bridge window %pR\n", res);

> @@ -159,8 +161,7 @@ static int __init pci_apply_final_quirks(void)
> u8 tmp;
>
> if (pci_cache_line_size)
> - printk(KERN_DEBUG "PCI: CLS %u bytes\n",
> - pci_cache_line_size << 2);
> + pr_info("CLS %u bytes\n", pci_cache_line_size << 2);
>
> pci_apply_fixup_final_quirks = true;
> for_each_pci_dev(dev) {
> @@ -177,7 +178,7 @@ static int __init pci_apply_final_quirks(void)
> if (!tmp || cls == tmp)
> continue;
>
> - printk(KERN_DEBUG "PCI: CLS mismatch (%u != %u), using %u bytes\n",
> + pr_info("CLS mismatch (%u != %u), using %u bytes\n",
> cls << 2, tmp << 2,
> pci_dfl_cache_line_size << 2);

Here's a case where we should actually be using pci_printk() since
this message is related to a specific device.

I added a new patch before your first patch to do this:

- printk(KERN_DEBUG "PCI: CLS mismatch ..."
+ pci_printk(KERN_DEBUG, dev, "CLS mismatch ..."

There's a similar case in pci_create_legacy_files(), so the new patch
converts both of those.

Bjorn

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