by Dmitry Torokhov

[permalink] [raw]

Subject: Re: [PATCH v2 09/10] MIPS: i8042: Probe this device only if it exists

On Wed, Jun 28, 2017 at 05:47:02PM +0200, Aleksandar Markovic wrote:
> From: Miodrag Dinic <[email protected]>
>
> ARCH_MIGHT_HAVE_PC_SERIO is selected by default for MIPS platforms.
> As a consequence SERIO_I8042 would be automatically selected for any
> MIPS board which wants to enable input support like keyboard
> (INPUT_KEYBOARD) regardless of i8042 controller existence.
>
> The dependency is as follows :
>
> config ARCH_MIGHT_HAVE_PC_SERIO [=y]
> Defined at drivers/input/serio/Kconfig:19
> Depends on: !UML
> Selected by: MIPS [=y]
>
> config SERIO
> Defined at drivers/input/serio/Kconfig:4
> default y
> Depends on: !UML
> Selected by: KEYBOARD_ATKBD [=y] && !UML && INPUT [=y] &&
> INPUT_KEYBOARD [=y]
>
> config SERIO_I8042
> Defined at drivers/input/serio/Kconfig:28
> tristate "i8042 PC Keyboard controller"
> default y
> Depends on: !UML && SERIO [=y] && ARCH_MIGHT_HAVE_PC_SERIO [=y]
> Selected by: KEYBOARD_ATKBD [=y] && !UML && INPUT [=y] &&
> INPUT_KEYBOARD [=y] && ARCH_MIGHT_HAVE_PC_SERIO [=y]
>
> If this driver probes the I8042_DATA_REG not knowing if the device
> exists it can cause a kernel to crash. Using check_legacy_ioport()
> interface we can selectively enable this driver only for the MIPS
> boards which actually have the i8042 controller.
>
> New "Ranchu" virtual platform does not support i8042 controller
> so it's added to the blacklist match table.
>
> Each MIPS machine should update this table with it's compatible strings
> if it does not support i8042 controller.
>
> In order to utilize this mechanism, each MIPS machine that do not
> have i8042 controller should update the blacklist table with its
> compatible strings.
>
> Signed-off-by: Miodrag Dinic <[email protected]>
> Signed-off-by: Goran Ferenc <[email protected]>
> Signed-off-by: Aleksandar Markovic <[email protected]>
> ---
> arch/mips/kernel/setup.c | 16 ++++++++++++++++
> drivers/input/serio/i8042-io.h | 2 +-
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
> index c22cde8..c3e0d2b 100644
> --- a/arch/mips/kernel/setup.c
> +++ b/arch/mips/kernel/setup.c
> @@ -79,6 +79,15 @@ const unsigned long mips_io_port_base = -1;
> EXPORT_SYMBOL(mips_io_port_base);
>
> /*
> + * Here we blacklist all MIPS boards which do not have i8042 controller
> + */
> +static const struct of_device_id i8042_blacklist_of_match[] = {
> + { .compatible = "mti,ranchu", },
> + {},
> +};
> +#define I8042_DATA_REG 0x60
> +
> +/*
> * Check for existence of legacy devices
> *
> * Some drivers may try to probe some I/O ports which can lead to
> @@ -90,9 +99,16 @@ EXPORT_SYMBOL(mips_io_port_base);
> */
> int check_legacy_ioport(unsigned long base_port)
> {
> + struct device_node *np;
> int ret = 0;
>
> switch (base_port) {
> + case I8042_DATA_REG:
> + np = of_find_matching_node(NULL, i8042_blacklist_of_match);
> + if (np)
> + ret = -ENODEV;
> + of_node_put(np);
> + break;

Can you simply mark 8042 region as busy when you are setting up the
board, so when i8042 tries to requets it it will fail?

> default:
> /* We will assume that the I/O device port exists if
> * not explicitly added to the blacklist match table
> diff --git a/drivers/input/serio/i8042-io.h b/drivers/input/serio/i8042-io.h
> index 34da81c..ec5fe9e 100644
> --- a/drivers/input/serio/i8042-io.h
> +++ b/drivers/input/serio/i8042-io.h
> @@ -72,7 +72,7 @@ static inline int i8042_platform_init(void)
> * On some platforms touching the i8042 data register region can do really
> * bad things. Because of this the region is always reserved on such boxes.
> */
> -#if defined(CONFIG_PPC)
> +#if defined(CONFIG_PPC) || defined(CONFIG_MIPS)
> if (check_legacy_ioport(I8042_DATA_REG))
> return -ENODEV;
> #endif
> --
> 2.7.4
>

Thanks.

--
Dmitry

2017-07-10 15:16:50

by Jonas Gorski

[permalink] [raw]

Subject: Re: [PATCH v2 09/10] MIPS: i8042: Probe this device only if it exists

Hi,

On 28 June 2017 at 17:47, Aleksandar Markovic
<[email protected]> wrote:
> From: Miodrag Dinic <[email protected]>
>
> ARCH_MIGHT_HAVE_PC_SERIO is selected by default for MIPS platforms.
> As a consequence SERIO_I8042 would be automatically selected for any
> MIPS board which wants to enable input support like keyboard
> (INPUT_KEYBOARD) regardless of i8042 controller existence.
>
> The dependency is as follows :
>
> config ARCH_MIGHT_HAVE_PC_SERIO [=y]
> Defined at drivers/input/serio/Kconfig:19
> Depends on: !UML
> Selected by: MIPS [=y]
>
> config SERIO
> Defined at drivers/input/serio/Kconfig:4
> default y
> Depends on: !UML
> Selected by: KEYBOARD_ATKBD [=y] && !UML && INPUT [=y] &&
> INPUT_KEYBOARD [=y]
>
> config SERIO_I8042
> Defined at drivers/input/serio/Kconfig:28
> tristate "i8042 PC Keyboard controller"
> default y
> Depends on: !UML && SERIO [=y] && ARCH_MIGHT_HAVE_PC_SERIO [=y]
> Selected by: KEYBOARD_ATKBD [=y] && !UML && INPUT [=y] &&
> INPUT_KEYBOARD [=y] && ARCH_MIGHT_HAVE_PC_SERIO [=y]
>
> If this driver probes the I8042_DATA_REG not knowing if the device
> exists it can cause a kernel to crash. Using check_legacy_ioport()
> interface we can selectively enable this driver only for the MIPS
> boards which actually have the i8042 controller.
>
> New "Ranchu" virtual platform does not support i8042 controller
> so it's added to the blacklist match table.
>
> Each MIPS machine should update this table with it's compatible strings
> if it does not support i8042 controller.
>
> In order to utilize this mechanism, each MIPS machine that do not
> have i8042 controller should update the blacklist table with its
> compatible strings.
>
> Signed-off-by: Miodrag Dinic <[email protected]>
> Signed-off-by: Goran Ferenc <[email protected]>
> Signed-off-by: Aleksandar Markovic <[email protected]>
> ---
> arch/mips/kernel/setup.c | 16 ++++++++++++++++
> drivers/input/serio/i8042-io.h | 2 +-
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
> index c22cde8..c3e0d2b 100644
> --- a/arch/mips/kernel/setup.c
> +++ b/arch/mips/kernel/setup.c
> @@ -79,6 +79,15 @@ const unsigned long mips_io_port_base = -1;
> EXPORT_SYMBOL(mips_io_port_base);
>
> /*
> + * Here we blacklist all MIPS boards which do not have i8042 controller
> + */
> +static const struct of_device_id i8042_blacklist_of_match[] = {
> + { .compatible = "mti,ranchu", },
> + {},
> +};
> +#define I8042_DATA_REG 0x60
> +
> +/*
> * Check for existence of legacy devices
> *
> * Some drivers may try to probe some I/O ports which can lead to
> @@ -90,9 +99,16 @@ EXPORT_SYMBOL(mips_io_port_base);
> */
> int check_legacy_ioport(unsigned long base_port)
> {
> + struct device_node *np;
> int ret = 0;
>
> switch (base_port) {
> + case I8042_DATA_REG:
> + np = of_find_matching_node(NULL, i8042_blacklist_of_match);
> + if (np)
> + ret = -ENODEV;
> + of_node_put(np);
> + break;

Wouldn't it make more sense to require boards to describe their i8042
device(s) in device tree if USE_OF is enabled? And maybe a whitelist
for those preexisting ones that don't. Much less maintenance overhead
for new boards, as I suspect the amount of boards with i8042 support
is much less than those that don't.

At least PowerPC seems to do it this way.

Regards
Jonas