PCI: Remove redundant TTL variable initialization

[PATCH] PCI: Remove redundant TTL variable initialization

Posted by Hans Zhang 3 months, 3 weeks ago

The local variables `ttl` were initialized to PCI_FIND_CAP_TTL but never
actually used. The loop termination condition is inherently controlled
by the TTL mechanism inside the PCI_FIND_NEXT_CAP_TTL macro, which already
ensures protection against infinite loops.

Remove these redundant operations to simplify the code and eliminate
potential logical ambiguities. This change does not affect functionality,
as the TTL safeguard is properly implemented within the macro.

Signed-off-by: Hans Zhang <18255117159@163.com>
---
- Submissions based on the following patches:
https://patchwork.kernel.org/project/linux-pci/patch/20250607161405.808585-1-18255117159@163.com/

Recently, I checked the code and found that there are still some areas that can be further optimized.
The above series of patches has been around for a long time, so I'm sending this one out for review
as a separate patch.
---
 drivers/pci/quirks.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index d7f4ee634263..50d0f193e4a3 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -2742,10 +2742,10 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, 0x9601, quirk_amd_780_apc_msi);
  */
 static int msi_ht_cap_enabled(struct pci_dev *dev)
 {
-	int pos, ttl = PCI_FIND_CAP_TTL;
+	int pos;
 
 	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
-	while (pos && ttl--) {
+	while (pos) {
 		u8 flags;
 
 		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
@@ -2796,10 +2796,10 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_CK804_PCIE,
 /* Force enable MSI mapping capability on HT bridges */
 static void ht_enable_msi_mapping(struct pci_dev *dev)
 {
-	int pos, ttl = PCI_FIND_CAP_TTL;
+	int pos;
 
 	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
-	while (pos && ttl--) {
+	while (pos) {
 		u8 flags;
 
 		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
@@ -2935,12 +2935,11 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_NVIDIA,
 
 static int ht_check_msi_mapping(struct pci_dev *dev)
 {
-	int pos, ttl = PCI_FIND_CAP_TTL;
-	int found = 0;
+	int pos, found = 0;
 
 	/* Check if there is HT MSI cap or enabled on this device */
 	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
-	while (pos && ttl--) {
+	while (pos) {
 		u8 flags;
 
 		if (found < 1)
@@ -3060,10 +3059,10 @@ static void nv_ht_enable_msi_mapping(struct pci_dev *dev)
 
 static void ht_disable_msi_mapping(struct pci_dev *dev)
 {
-	int pos, ttl = PCI_FIND_CAP_TTL;
+	int pos;
 
 	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
-	while (pos && ttl--) {
+	while (pos) {
 		u8 flags;
 
 		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,

base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
-- 
2.25.1

Re: [PATCH] PCI: Remove redundant TTL variable initialization

Posted by Hans Zhang 1 month, 3 weeks ago

Dear Bjorn,

Because of this series, you have accepted it.
https://patchwork.kernel.org/project/linux-pci/cover/20250813144529.303548-1-18255117159@163.com/

It is already in the following branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/log/?h=capability-search


But I saw the status of patch as "Not Applicable". Is it necessary for 
me to remake the v2 version based on v6.17-rc1? Or is this patch 
unreasonable?

Best regards,
Hans

On 2025/6/16 23:24, Hans Zhang wrote:
> The local variables `ttl` were initialized to PCI_FIND_CAP_TTL but never
> actually used. The loop termination condition is inherently controlled
> by the TTL mechanism inside the PCI_FIND_NEXT_CAP_TTL macro, which already
> ensures protection against infinite loops.
> 
> Remove these redundant operations to simplify the code and eliminate
> potential logical ambiguities. This change does not affect functionality,
> as the TTL safeguard is properly implemented within the macro.
> 
> Signed-off-by: Hans Zhang <18255117159@163.com>
> ---
> - Submissions based on the following patches:
> https://patchwork.kernel.org/project/linux-pci/patch/20250607161405.808585-1-18255117159@163.com/
> 
> Recently, I checked the code and found that there are still some areas that can be further optimized.
> The above series of patches has been around for a long time, so I'm sending this one out for review
> as a separate patch.
> ---
>   drivers/pci/quirks.c | 17 ++++++++---------
>   1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index d7f4ee634263..50d0f193e4a3 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -2742,10 +2742,10 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, 0x9601, quirk_amd_780_apc_msi);
>    */
>   static int msi_ht_cap_enabled(struct pci_dev *dev)
>   {
> -	int pos, ttl = PCI_FIND_CAP_TTL;
> +	int pos;
>   
>   	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
> -	while (pos && ttl--) {
> +	while (pos) {
>   		u8 flags;
>   
>   		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
> @@ -2796,10 +2796,10 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_CK804_PCIE,
>   /* Force enable MSI mapping capability on HT bridges */
>   static void ht_enable_msi_mapping(struct pci_dev *dev)
>   {
> -	int pos, ttl = PCI_FIND_CAP_TTL;
> +	int pos;
>   
>   	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
> -	while (pos && ttl--) {
> +	while (pos) {
>   		u8 flags;
>   
>   		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
> @@ -2935,12 +2935,11 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_NVIDIA,
>   
>   static int ht_check_msi_mapping(struct pci_dev *dev)
>   {
> -	int pos, ttl = PCI_FIND_CAP_TTL;
> -	int found = 0;
> +	int pos, found = 0;
>   
>   	/* Check if there is HT MSI cap or enabled on this device */
>   	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
> -	while (pos && ttl--) {
> +	while (pos) {
>   		u8 flags;
>   
>   		if (found < 1)
> @@ -3060,10 +3059,10 @@ static void nv_ht_enable_msi_mapping(struct pci_dev *dev)
>   
>   static void ht_disable_msi_mapping(struct pci_dev *dev)
>   {
> -	int pos, ttl = PCI_FIND_CAP_TTL;
> +	int pos;
>   
>   	pos = pci_find_ht_capability(dev, HT_CAPTYPE_MSI_MAPPING);
> -	while (pos && ttl--) {
> +	while (pos) {
>   		u8 flags;
>   
>   		if (pci_read_config_byte(dev, pos + HT_MSI_FLAGS,
> 
> base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494