[PATCH 4.19 08/99] i2c: Allow recovery of the initial IRQ by an I2C client device.

From: Greg Kroah-Hartman
Date: Mon May 06 2019 - 10:40:44 EST

From: Jim Broadus <jbroadus@xxxxxxxxx>

commit 93b6604c5a669d84e45fe5129294875bf82eb1ff upstream.

A previous change allowed I2C client devices to discover new IRQs upon
reprobe by clearing the IRQ in i2c_device_remove. However, if an IRQ was
assigned in i2c_new_device, that information is lost.

For example, the touchscreen and trackpad devices on a Dell Inspiron laptop
are I2C devices whose IRQs are defined by ACPI extended IRQ types. The
client device structures are initialized during an ACPI walk. After
removing the i2c_hid device, modprobe fails.

This change caches the initial IRQ value in i2c_new_device and then resets
the client device IRQ to the initial value in i2c_device_remove.

Fixes: 6f108dd70d30 ("i2c: Clear client->irq in i2c_device_remove")
Signed-off-by: Jim Broadus <jbroadus@xxxxxxxxx>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
Reviewed-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
[wsa: this is an easy to backport fix for the regression. We will
refactor the code to handle irq assignments better in general.]
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/i2c/i2c-core-base.c | 9 +++++----
include/linux/i2c.h | 1 +
2 files changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -430,7 +430,7 @@ static int i2c_device_remove(struct devi
device_init_wakeup(&client->dev, false);

- client->irq = 0;
+ client->irq = client->init_irq;

return status;
@@ -741,10 +741,11 @@ i2c_new_device(struct i2c_adapter *adap,
client->flags = info->flags;
client->addr = info->addr;

- client->irq = info->irq;
- if (!client->irq)
- client->irq = i2c_dev_irq_from_resources(info->resources,
+ client->init_irq = info->irq;
+ if (!client->init_irq)
+ client->init_irq = i2c_dev_irq_from_resources(info->resources,
+ client->irq = client->init_irq;

strlcpy(client->name, info->type, sizeof(client->name));

--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -333,6 +333,7 @@ struct i2c_client {
char name[I2C_NAME_SIZE];
struct i2c_adapter *adapter; /* the adapter we sit on */
struct device dev; /* the device structure */
+ int init_irq; /* irq set at initialization */
int irq; /* irq issued by device */
struct list_head detected;