[PATCH 0/2] w1: Search the SGI 1-wire buses only once

[PATCH 0/2] w1: Search the SGI 1-wire buses only once

[Imre Kaloz]

The slaves on the SGI 1-wire buses are soldered to the board, yet the
w1 core rescans each bus every 10 seconds, busy-waiting through the
time slots.

Patch 1 lets a bus master set its search count, and patch 2 has
sgi_w1 search once.

Tested on an Octane.

Imre Kaloz (2):
  w1: Let bus masters set the search count
  w1: sgi_w1: Search the bus only once

 drivers/w1/masters/sgi_w1.c | 3 +++
 drivers/w1/w1_int.c         | 3 +++
 include/linux/w1.h          | 5 +++++
 3 files changed, 11 insertions(+)


base-commit: 24a19b953e2a3d0ea5a8c4951a0ab8f32720c907
-- 
2.47.3

[PATCH 1/2] w1: Let bus masters set the search count

[Imre Kaloz]

A master whose slaves cannot change after probe gains nothing from
repeated searches. Let the master set the number of automatic searches
on its bus; zero keeps the search_count module parameter.

Signed-off-by: Imre Kaloz <kaloz@kernel.org>
---
 drivers/w1/w1_int.c | 3 +++
 include/linux/w1.h  | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/w1/w1_int.c b/drivers/w1/w1_int.c
index 19a0ea28e9f3..54c87927eb60 100644
--- a/drivers/w1/w1_int.c
+++ b/drivers/w1/w1_int.c
@@ -130,6 +130,9 @@ int w1_add_master_device(struct w1_bus_master *master)
 
 	memcpy(dev->bus_master, master, sizeof(struct w1_bus_master));
 
+	if (master->search_count)
+		dev->search_count = master->search_count;
+
 	dev->initialized = 1;
 
 	dev->thread = kthread_run(&w1_process, dev, "%s", dev->name);
diff --git a/include/linux/w1.h b/include/linux/w1.h
index 064805bfae3f..88c5299476ed 100644
--- a/include/linux/w1.h
+++ b/include/linux/w1.h
@@ -122,6 +122,9 @@ typedef void (*w1_slave_found_callback)(struct w1_master *, u64);
  * @dev_id: Optional device id string, which w1 slaves could use for
  * creating names, which then give a connection to the w1 master
  *
+ * @search_count: Optional number of automatic searches to run on this
+ * bus, -1 for unlimited; 0 uses the search_count module parameter
+ *
  * Note: read_bit and write_bit are very low level functions and should only
  * be used with hardware that doesn't really support 1-wire operations,
  * like a parallel/serial port.
@@ -156,6 +159,8 @@ struct w1_bus_master {
 		u8, w1_slave_found_callback);
 
 	char		*dev_id;
+
+	int		search_count;
 };
 
 /**
-- 
2.47.3

[PATCH 2/2] w1: sgi_w1: Search the bus only once

[Imre Kaloz]

The slaves on this bus are soldered to the board, so rescanning it
every timeout period only busy-waits through the time slots.

Signed-off-by: Imre Kaloz <kaloz@kernel.org>
---
 drivers/w1/masters/sgi_w1.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/w1/masters/sgi_w1.c b/drivers/w1/masters/sgi_w1.c
index 48c10062022c..a583821d2421 100644
--- a/drivers/w1/masters/sgi_w1.c
+++ b/drivers/w1/masters/sgi_w1.c
@@ -90,6 +90,9 @@ static int sgi_w1_probe(struct platform_device *pdev)
 	sdev->bus_master.reset_bus = sgi_w1_reset_bus;
 	sdev->bus_master.touch_bit = sgi_w1_touch_bit;
 
+	/* The slaves are soldered on; one search finds them all. */
+	sdev->bus_master.search_count = 1;
+
 	pdata = dev_get_platdata(&pdev->dev);
 	if (pdata) {
 		strscpy(sdev->dev_id, pdata->dev_id, sizeof(sdev->dev_id));
-- 
2.47.3

Re: [PATCH 0/2] w1: Search the SGI 1-wire buses only once

[Krzysztof Kozlowski]

On Tue, 13 Oct 2026 11:50:44 +0200, Imre Kaloz wrote:
> The slaves on the SGI 1-wire buses are soldered to the board, yet the
> w1 core rescans each bus every 10 seconds, busy-waiting through the
> time slots.
> 
> Patch 1 lets a bus master set its search count, and patch 2 has
> sgi_w1 search once.
> 
> [...]

Applied, thanks!

[1/2] w1: Let bus masters set the search count
      https://git.kernel.org/krzk/linux-w1/c/c6c851e7499ebd075590a6c1ed1a707cf05f4058
[2/2] w1: sgi_w1: Search the bus only once
      https://git.kernel.org/krzk/linux-w1/c/e8bb5d130f2592632897aaa8e4e05a908a4847d6

Best regards,
-- 
Krzysztof Kozlowski <krzk@kernel.org>