[PATCH v4] Input: sysrq - DT binding for key sequence

[Mathieu Poirier]

On 15 July 2013 20:43, Rob Herring <robherring2 at gmail.com> wrote:

> On 07/15/2013 10:36 AM, mathieu.poirier at linaro.org wrote:
> > From: "Mathieu J. Poirier" <mathieu.poirier at linaro.org>
> >
> > Adding a simple device tree binding for the specification of key
> sequences.
> > Definition of the keys found in the sequence are located in
> > 'include/uapi/linux/input.h'.
> >
> > For the sysrq driver, holding the sequence of keys down for a specific
> amount of time
> > will reset the system.
> >
> > Signed-off-by: Mathieu Poirier <mathieu.poirier at linaro.org>
> > ---
> > changes for v4:
> >   - Moved seach of reset sequence nodes to a single call.
> > ---
> >  .../devicetree/bindings/input/input-reset.txt      | 34 ++++++++++++++
> >  drivers/tty/sysrq.c                                | 54
> ++++++++++++++++++++++
> >  2 files changed, 88 insertions(+)
> >  create mode 100644
> Documentation/devicetree/bindings/input/input-reset.txt
> >
> > diff --git a/Documentation/devicetree/bindings/input/input-reset.txt
> b/Documentation/devicetree/bindings/input/input-reset.txt
> > new file mode 100644
> > index 0000000..79504af
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/input/input-reset.txt
> > @@ -0,0 +1,34 @@
> > +Input: sysrq reset sequence
> > +
> > +A simple binding to represent a set of keys as described in
> > +include/uapi/linux/input.h.  This is to communicate a
> > +sequence of keys to the sysrq driver.  Upon holding the keys
> > +for a specified amount of time (if specified) the system is
> > +sync'ed and reset.
> > +
> > +Key sequences are global to the system but all the keys in a
> > +set must be coming from the same input device.
> > +
> > +The /chosen node should contain a 'linux,sysrq-reset-seq' child
> > +node to define a set of keys.
> > +
> > +Required property:
> > +sysrq-reset-seq: array of keycodes
> > +
> > +Optional property:
> > +timeout-ms: duration keys must be pressed together in microseconds
>
> milliseconds (ms) or microseconds (us)?
>
>
Right, milliseconds.


> > +before generating a sysrq
> > +
> > +Example:
> > +
> > + chosen {
> > +                linux,sysrq-reset-seq {
> > +                        keyset = <0x03
> > +                                  0x04
> > +                                  0x0a>;
> > +                        timeout-ms = <3000>;
> > +                };
> > +         };
> > +
> > +Would represent KEY_2, KEY_3 and KEY_9.
> > +
> > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> > index b51c154..01a8729 100644
> > --- a/drivers/tty/sysrq.c
> > +++ b/drivers/tty/sysrq.c
> > @@ -44,6 +44,7 @@
> >  #include <linux/uaccess.h>
> >  #include <linux/moduleparam.h>
> >  #include <linux/jiffies.h>
> > +#include <linux/of.h>
> >
> >  #include <asm/ptrace.h>
> >  #include <asm/irq_regs.h>
> > @@ -671,6 +672,50 @@ static void sysrq_detect_reset_sequence(struct
> sysrq_state *state,
> >       }
> >  }
> >
> > +static void sysrq_of_get_keyreset_config(void)
> > +{
> > +     unsigned short key;
> > +     struct device_node *np;
> > +     const struct property *prop;
> > +     const __be32 *val;
> > +     int count, i;
> > +
> > +     np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
> > +     if (!np) {
> > +             pr_debug("No sysrq node found");
> > +             goto out;
> > +     }
> > +
> > +     prop = of_find_property(np, "keyset", NULL);
> > +     if (!prop || !prop->value) {
> > +             pr_err("Invalid input keyset");
> > +             goto out;
> > +     }
> > +
> > +     count = prop->length / sizeof(u32);
> > +     val = prop->value;
>
> None of the existing helpers to retrieve property arrays doesn't work here?
>

The problem here is that we never know how long the sequence will be.  As
such the 'of_property_read_uXY_array' functions won't work.  Or maybe
you're referring to another set of helpers... If so, please clarify.


>
> > +
> > +     if (count > SYSRQ_KEY_RESET_MAX)
> > +             count = SYSRQ_KEY_RESET_MAX;
> > +
> > +     /* reset in case a __weak definition was present */
> > +     sysrq_reset_seq_len = 0;
> > +
> > +     for (i = 0; i < count; i++) {
> > +             key = (unsigned short)be32_to_cpup(val++);
> > +             if (key == KEY_RESERVED || key > KEY_MAX)
> > +                     break;
> > +
> > +             sysrq_reset_seq[sysrq_reset_seq_len++] = key;
> > +     }
> > +
> > +     /* get reset timeout if any */
> > +     of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
> > +
> > + out:
> > +     ;
> > +}
> > +
> >  static void sysrq_reinject_alt_sysrq(struct work_struct *work)
> >  {
> >       struct sysrq_state *sysrq =
> > @@ -688,6 +733,7 @@ static void sysrq_reinject_alt_sysrq(struct
> work_struct *work)
> >               input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
> >               input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
> >
> > +
>
> spurious ws change


> >               input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
> >               input_inject_event(handle, EV_KEY, alt_code, 0);
> >               input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
> > @@ -903,6 +949,7 @@ static inline void sysrq_register_handler(void)
> >       int error;
> >       int i;
> >
> > +     /* first check if a __weak interface was instantiated */
> >       for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
> >               key = platform_sysrq_reset_seq[i];
> >               if (key == KEY_RESERVED || key > KEY_MAX)
> > @@ -911,6 +958,13 @@ static inline void sysrq_register_handler(void)
> >               sysrq_reset_seq[sysrq_reset_seq_len++] = key;
> >       }
> >
> > +     /*
> > +      * DT configuration takes precedence over anything
> > +      * that would have been defined via the __weak
> > +      * interface
> > +      */
> > +     sysrq_of_get_keyreset_config();
> > +
> >       error = input_register_handler(&sysrq_handler);
> >       if (error)
> >               pr_err("Failed to register input handler, error %d",
> error);
> >
>
>
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