Hi Pradeep, 

I think the following command doesn't work to you:

echo 5 > /sys/class/backlight/acpi_video0/brightness

It the above command not work, that means EC didn't change backlight
value:

Method (_BCM, 1, NotSerialized)
{
    Divide (Arg0, 0x0A, Local0, Local1)
    Decrement (Local1)
    Store (Local1, ^^^^LPC.EC0.BRTS)	<== write backlight value to EC register
}

Per my understood, EC firmware should change brightness but didn't do that, another
way is touch i915 register in _BCM.

Acer machine provide a broken _BCM implementation and they didn't test it.


Thanks a lot!
Joey Lee

於 二，2012-03-13 於 09:12 -0400，Pradeep Subrahmanion 提到：

Hi Joey, 

yes , /sys/class/backlight/intel_backlight exists . I tried giving
acpi_backlight=vendor in grub config.Hot keys works like earlier.But
increasing brightness after maximum levels give blank screen(like
earlier). 

I have attached acpidump.
 
----
Thanks  , 
 
Pradeep Subrahmanion

On Tue, 2012-03-13 at 11:10 +0800, joeyli wrote:

quoted

Hi Pradeep, 

於 日，2012-03-11 於 19:42 +0000，Florian Tobias Schandinat 提到：

quoted

Hi,

On 03/11/2012 06:21 PM, Pradeep Subrahmanion wrote:

quoted

Hi ,

         Brightness control was not  working on Acer Aspire 4736 using
default ACPI interface.  acer-acpi also do not support 4730 series since
it uses new WMI interface.
This driver adds brightness control by accessing the LBB PCI
configuration register. This approach may also work on other laptops in
4730 series .But currently ,  it is only tested  for 
Aspire 4736.  

Pleae check does there have following interface?

/sys/class/backlight/intel_backlight

And,
did you try kernel parameter "acpi_backlight=vendor", does it work to
you?

Please attach acpidump: acpidump > acpidump.dat


Thanks
Joey Lee

quoted

quoted

From 893031c1e9bdefd9642b98825062b5df98af0d77 Mon Sep 17 00:00:00 2001
From: Pradeep Subrahmanion <subrahmanion.pradeep@gmail.com
<mailto:subrahmanion.pradeep@gmail.com>>
Date: Sun, 11 Mar 2012 23:11:23 -0400
Subject: [PATCH] Added backlight driver for Acer Aspire 4736

the commit message should be here, I think.

quoted

Signed-off-by: Pradeep Subrahmanion <subrahmanion.pradeep@gmail.com
<mailto:subrahmanion.pradeep@gmail.com>>

Please resend this email in the correct format: As you can see in my
email the text version of your patch is severely screwed up and nobody
wants to even try converting a HTML format to a proper patch again,
probably most people won't even receive an email that has a HTML part as
their spam filter are going to handle it as spam. git send-email will
take care of it for you if you configure it for your account.
You should also cc Andrew Morton [off-list ref] as he's the
one who handles backlight patches at the moment.


Best regards,

Florian Tobias Schandinat

quoted

---
 drivers/video/backlight/acer4736_bl.c |  110
+++++++++++++++++++++++++++++++++
 1 files changed, 110 insertions(+), 0 deletions(-)
 create mode 100644 drivers/video/backlight/acer4736_bl.c

diff --git a/drivers/video/backlight/acer4736_bl.c

b/drivers/video/backlight/acer4736_bl.c
new file mode 100644
index 0000000..6fe2937

--- /dev/null
+++ b/drivers/video/backlight/acer4736_bl.c

@@ -0,0 +1,110 @@
+/*
+ * Backlight driver for Acer Aspire 4736
+ *
+ * Copyright (C) Pradeep Subrahmanion <subrahmanion.pradeep@gmail.com

<mailto:subrahmanion.pradeep@gmail.com>>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This driver uses LBB PCI configuration register to change the
+ * backlight brightness.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/dmi.h>
+#include <linux/io.h>
+#include <linux/pci.h>
+
+static u8 max_brightness = 0xFF;
+static u8 lbb_offset =  0xF4;
+static unsigned int device_id = 0x2a42;
+static unsigned int vendor_id = 0x8086;
+
+struct backlight_device *acer_backlight_device;
+struct pci_dev *pdev;
+
+static int acer_dmi_match(const struct dmi_system_id *id)
+{
+ printk(KERN_INFO "acer4736_bl: %s detected\n", id->ident);
+ return 1;
+}
+
+static const struct dmi_system_id __initdata acer_device_table[] = {
+{
+ .callback = acer_dmi_match,
+ .ident = "Aspire 4736",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+ DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 4736"),
+ },
+ },
+ {}
+};
+static int read_brightness(struct backlight_device *bd)
+{
+ u8 result;
+ pci_read_config_byte(pdev, lbb_offset, &result);
+ return result;
+}
+
+static int update_brightness(struct backlight_device *bd)
+{
+ u8 intensity = bd->props.brightness;
+ if (intensity > max_brightness) {
+ printk(KERN_INFO "Acer4736_bl: Invalid parameter. Maximum value is %d"
+ , max_brightness);
+ return -1;
+ }
+ pci_write_config_byte(pdev, lbb_offset, intensity);
+ return 0;
+}
+static const struct  backlight_ops acer_backlight_ops = {
+ .get_brightness = read_brightness,
+ .update_status  = update_brightness,
+};
+
+static int __init acer4736_bl_init(void)
+{
+ struct backlight_properties props;
+ if (!dmi_check_system(acer_device_table))
+ return -ENODEV;
+
+ pdev = pci_get_device(vendor_id, device_id, NULL);
+
+ if (!pdev)
+ return -ENODEV;
+
+ printk(KERN_INFO "Loading Acer 4736 backlight driver\n");
+ memset(&props, 0, sizeof(struct backlight_properties));
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = max_brightness;
+
+ acer_backlight_device = backlight_device_register("acer_backlight",
+ NULL, NULL, &acer_backlight_ops, &props);
+ acer_backlight_device->props.max_brightness = max_brightness;
+ acer_backlight_device->props.brightness  > > > > + read_brightness(acer_backlight_device);
+ backlight_update_status(acer_backlight_device);
+
+ return 0;
+}
+
+static void __exit acer4736_bl_exit(void)
+{
+ pci_dev_put(pdev);
+ backlight_device_unregister(acer_backlight_device);
+}
+
+module_init(acer4736_bl_init);
+module_exit(acer4736_bl_exit);
+
+MODULE_AUTHOR("Pradeep Subrahmanion <subrahmanion.pradeep@gmail.com
<mailto:subrahmanion.pradeep@gmail.com>>");
+MODULE_DESCRIPTION("Acer Aspire 4736 Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(dmi, acer_device_table);
-- 
1.7.2.5

-------------  

Pradeep Subrahmanion

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