[PATCH] w1: add fast search for single slave bus

[PATCH] w1: add fast search for single slave bus

[Hubert Feurstein]

This enables a much more efficient way of device searching. It uses the
1-wire read-rom operation which allows the direct reading of the slave
address. BUT this works only with exactly one slave on the bus.

Signed-off-by: Hubert Feurstein <h.feurstein@gmail.com>
---
 drivers/w1/Kconfig |    8 ++++++++
 drivers/w1/w1.c    |   11 +++++++++++
 2 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/drivers/w1/Kconfig b/drivers/w1/Kconfig
index fd2c7bd..e5006bc 100644
--- a/drivers/w1/Kconfig
+++ b/drivers/w1/Kconfig
@@ -25,6 +25,14 @@ config W1_CON
 	  2. Userspace commands. Includes read/write and search/alarm search commands.
 	  3. Replies to userspace commands.
 
+config W1_FAST_SEARCH
+	bool "Fast search (single slave bus only!)"
+	---help---
+	  This enables a much more efficient way of device searching. It uses the
+	  1-wire read-rom operation which allows the direct reading of the slave
+	  address. BUT this works only with exactly one slave on the bus.
+	  If unsure, say 'N'.
+
 source drivers/w1/masters/Kconfig
 source drivers/w1/slaves/Kconfig
 
diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index c374978..7c648ec 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -892,6 +892,17 @@ void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb
 			break;
 		}
 
+#ifdef CONFIG_W1_FAST_SEARCH
+		if (dev->max_slave_count == 1) {
+			w1_write_8(dev, W1_READ_ROM);
+
+			if (w1_read_block(dev, (u8 *)&rn, 8) == 8 && rn)
+				cb(dev, rn);
+
+			break;
+		}
+#endif
+
 		/* Start the search */
 		w1_write_8(dev, search_type);
 		for (i = 0; i < 64; ++i) {
-- 
1.7.4.1

Re: [PATCH] w1: add fast search for single slave bus

[Evgeniy Polyakov]

Hi

On Mon, Nov 28, 2011 at 09:06:47PM +0100, Hubert Feurstein (h.feurstein@gmail.com) wrote:
> This enables a much more efficient way of device searching. It uses the
> 1-wire read-rom operation which allows the direct reading of the slave
> address. BUT this works only with exactly one slave on the bus.

Although idea may sound resonable, kernel is shipped with only one
compiled option, and it is quite uncommon to recompile them.
So this option will unlikely to be enabled. I would recommend to add
either a module parameter to forbid multiple slave devices and use fast
search, or use fast search when only one device exists and switch to
common search when it fails (if it is possible to detect that there are
multiple devices on the bus using fast search)

-- 
	Evgeniy Polyakov

Re: [PATCH] w1: add fast search for single slave bus

[Jean-François Dagenais]

On 2011-11-28, at 15:06, Hubert Feurstein wrote:

> This enables a much more efficient way of device searching. It uses the
> 1-wire read-rom operation which allows the direct reading of the slave
> address. BUT this works only with exactly one slave on the bus.
> 
> Signed-off-by: Hubert Feurstein <h.feurstein@gmail.com>
> ---
> drivers/w1/Kconfig |    8 ++++++++
> drivers/w1/w1.c    |   11 +++++++++++
> 2 files changed, 19 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/w1/Kconfig b/drivers/w1/Kconfig
> index fd2c7bd..e5006bc 100644
> --- a/drivers/w1/Kconfig
> +++ b/drivers/w1/Kconfig
> @@ -25,6 +25,14 @@ config W1_CON
> 	  2. Userspace commands. Includes read/write and search/alarm search commands.
> 	  3. Replies to userspace commands.
> 
> +config W1_FAST_SEARCH
> +	bool "Fast search (single slave bus only!)"
> +	---help---
> +	  This enables a much more efficient way of device searching. It uses the
> +	  1-wire read-rom operation which allows the direct reading of the slave
> +	  address. BUT this works only with exactly one slave on the bus.
> +	  If unsure, say 'N'.
> +
Not needed I think, see below...
> source drivers/w1/masters/Kconfig
> source drivers/w1/slaves/Kconfig
> 
> diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
> index c374978..7c648ec 100644
> --- a/drivers/w1/w1.c
> +++ b/drivers/w1/w1.c
> @@ -892,6 +892,17 @@ void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb
> 			break;
> 		}
> 
> +#ifdef CONFIG_W1_FAST_SEARCH
> +		if (dev->max_slave_count == 1) {
> +			w1_write_8(dev, W1_READ_ROM);
> +
> +			if (w1_read_block(dev, (u8 *)&rn, 8) == 8 && rn)
> +				cb(dev, rn);
> +
> +			break;
> +		}
> +#endif
> +
I would drop the CONFIG item and just add this "if" block to the search function
unconditionnaly. Unless I am missing something, it wouldn't hurt multi-slave setups...
> 		/* Start the search */
> 		w1_write_8(dev, search_type);
> 		for (i = 0; i < 64; ++i) {
> -- 
> 1.7.4.1
> 
> --
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[PATCH v2] w1: add fast search for single slave bus

[Hubert Feurstein]

This enables a much more efficient way of device searching. It uses the
1-wire read-rom operation which allows the direct reading of the slave
address. BUT this works only with exactly one slave on the bus.

Signed-off-by: Hubert Feurstein <h.feurstein@gmail.com>
---
 v2: remove config option

 drivers/w1/w1.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index c374978..9761950 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -892,6 +892,16 @@ void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb
 			break;
 		}
 
+		/* Do fast search on single slave bus */
+		if (dev->max_slave_count == 1) {
+			w1_write_8(dev, W1_READ_ROM);
+
+			if (w1_read_block(dev, (u8 *)&rn, 8) == 8 && rn)
+				cb(dev, rn);
+
+			break;
+		}
+
 		/* Start the search */
 		w1_write_8(dev, search_type);
 		for (i = 0; i < 64; ++i) {
-- 
1.7.7.4

Re: [PATCH v2] w1: add fast search for single slave bus

[Evgeniy Polyakov]

Hi

On Sun, Dec 04, 2011 at 05:46:50PM +0100, Hubert Feurstein (h.feurstein@gmail.com) wrote:
> This enables a much more efficient way of device searching. It uses the
> 1-wire read-rom operation which allows the direct reading of the slave
> address. BUT this works only with exactly one slave on the bus.

Looks good to me, thank you!
Greg, please pull it into your tree

> Signed-off-by: Hubert Feurstein <h.feurstein@gmail.com>

Acked-by: Evgeniy Polyakov <zbr@ioremap.net>

-- 
	Evgeniy Polyakov

Re: [PATCH v2] w1: add fast search for single slave bus

[Greg KH]

On Mon, Dec 05, 2011 at 03:29:31PM +0300, Evgeniy Polyakov wrote:
> Hi
> 
> On Sun, Dec 04, 2011 at 05:46:50PM +0100, Hubert Feurstein (h.feurstein@gmail.com) wrote:
> > This enables a much more efficient way of device searching. It uses the
> > 1-wire read-rom operation which allows the direct reading of the slave
> > address. BUT this works only with exactly one slave on the bus.
> 
> Looks good to me, thank you!
> Greg, please pull it into your tree

Um, pull what?  Can someone please send me the whole patch, as I can't
seem to find it anywhere, sorry.

greg k-h

Re: [PATCH v2] w1: add fast search for single slave bus

[Evgeniy Polyakov]

On Fri, Dec 09, 2011 at 04:00:54PM -0800, Greg KH (greg@kroah.com) wrote:
> Um, pull what?  Can someone please send me the whole patch, as I can't
> seem to find it anywhere, sorry.

Forwarded

-- 
	Evgeniy Polyakov