Re: [PATCH] misc/pca9552: Add qom set and get

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 11/19/19 5:27 PM, Cédric Le Goater wrote:
> On 18/11/2019 18:48, Philippe Mathieu-Daudé wrote:
>> Odd... I only received Cédric answer, not Joel patch.
>>
>> On 11/18/19 11:00 AM, Cédric Le Goater wrote:
>>> On 18/11/2019 07:17, Joel Stanley wrote:
>>>> Following the pattern of the work recently done with the ASPEED GPIO
>>>> model, this adds support for inspecting and modifying the PCA9552 LEDs
>>>> from the monitor.
>>>>
>>>>    (qemu) qom-set  /machine/unattached/device[17] led0 on
>>>>    (qemu) qom-get  /machine/unattached/device[17] led0
>>>>    "on"
>>>>
>>>>    (qemu) qom-set  /machine/unattached/device[17] led0 off
>>>>    (qemu) qom-get  /machine/unattached/device[17] led0
>>>>    "off"
>>>>
>>>>    (qemu) qom-set  /machine/unattached/device[17] led0 pwm0
>>>>    (qemu) qom-get  /machine/unattached/device[17] led0
>>>>    "pwm0"
>>>>
>>>>    (qemu) qom-set  /machine/unattached/device[17] led0 pwm1
>>>>    (qemu) qom-get  /machine/unattached/device[17] led0
>>>>    "pwm1"
>>>
>>> It would be nice to revive the QOM get patchset from David.
>>>
>>>      http://patchwork.ozlabs.org/patch/666458/
>>>
>>> Did we reach some consensus ?
>>>
>>>> Signed-off-by: Joel Stanley <joel@jms.id.au>
>>>
>>> Some comments below.
>>>
>>>> ---
>>>> The qom device in mainline qemu is a different path. Using the monitor
>>>> examine `info qom-tree /machine/unattached/` to discover it.
>>>>
>>>> This can be tested with a Witherspoon image.
>>>>
>>>> $ wget https://openpower.xyz/job/openbmc-build/distro=ubuntu,label=builder,target=witherspoon/lastSuccessfulBuild/artifact/deploy/images/witherspoon/obmc-phosphor-image-witherspoon.ubi.mtd
>>>>
>>>> $ qemu-system-arm -M witherspoon-bmc -serial pty -monitor pty -nographic \
>>>>    -drive file=obmc-phosphor-image-witherspoon.ubi.mtd,format=raw,if=mtd
>>>> char device redirected to /dev/pts/5 (label compat_monitor0)
>>>> char device redirected to /dev/pts/10 (label serial0)
>>>>
>>>> $ screen /dev/pts/5
>>>> QEMU 4.1.91 monitor - type 'help' for more information
>>>> (qemu) qom-get  /machine/unattached/device[17] led0
>>>> "off"
>>>>
>>>> $ screen /dev/pts/19
>>>> root@witherspoon:~# cd /sys/class/gpio/
>>>> root@witherspoon:/sys/class/gpio# echo 248 > export
>>>> root@witherspoon:/sys/class/gpio# cat gpio248/value
>>>> 0
>>>>
>>>> (qemu) qom-set  /machine/unattached/device[17] led0 on
>>>>
>>>> root@witherspoon:/sys/class/gpio# echo out > gpio248/direction
>>>> root@witherspoon:/sys/class/gpio# cat gpio248/value
>>>> 1
>>>>
>>>> (qemu) qom-get  /machine/unattached/device[17] led0
>>>> "on"
>>>>
>>>> (qemu) qom-set  /machine/unattached/device[17] led0 off
>>>> (qemu) qom-get  /machine/unattached/device[17] led0
>>>> "off"
>>>>
>>>> root@witherspoon:/sys/class/gpio# cat gpio248/value
>>>> 0
>>
>> I am assuming this is 5.0 material.
>>
>> This is a good starting point, and is useful.
>>
>> However this would be useful for other boards/devices too.
>>
>> What about defining a InterfaceInfo[] for external GPIOs?
> 
> The code below is very specific to pca9552.

Yes, sorry if I was unclear, I don't want to delay this series, I was 
just thinking about other uses.

> What kind of interface do you have in mind more precisely ?
> which handlers ?

Here we expose the devices GPIOs (as output) so they can be modified via 
QMP.

A QMP client could subscribe to GPIOs input events (or IRQ triggered).

(The PCA9552 can also use the 16 lines as input, but Joel added a "input 
line behaviour not modeled" comment below).

Maybe the PCA9552 isn't the best example for my generic use case, 
because it is already "out of the soc/board" being on a bus.

I'm more concerned about a generic QMP way to access GPIOs from a SoC 
exposed to a physical user of a board.

>> Shouldn't we use the qemu_irq type for that then?
>>
>>>>
>>>> Signed-off-by: Joel Stanley <joel@jms.id.au>
>>>> ---
>>>>    hw/misc/pca9552.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++
>>>>    1 file changed, 91 insertions(+)
>>>>
>>>> diff --git a/hw/misc/pca9552.c b/hw/misc/pca9552.c
>>>> index 73be28d9369c..0362aac8c862 100644
>>>> --- a/hw/misc/pca9552.c
>>>> +++ b/hw/misc/pca9552.c
>>>> @@ -15,12 +15,16 @@
>>>>    #include "hw/misc/pca9552.h"
>>>>    #include "hw/misc/pca9552_regs.h"
>>>>    #include "migration/vmstate.h"
>>>> +#include "qapi/error.h"
>>>> +#include "qapi/visitor.h"
>>>>      #define PCA9552_LED_ON   0x0
>>>>    #define PCA9552_LED_OFF  0x1
>>>>    #define PCA9552_LED_PWM0 0x2
>>>>    #define PCA9552_LED_PWM1 0x3
>>>>    +static const char *led_state[] = {"on", "off", "pwm0", "pwm1"};
>>
>> BTW "pwm0/pwm1" as "state" is confuse, but I understand this is how the PCA9552 datasheet describes it.
>>
>>>> +
>>>>    static uint8_t pca9552_pin_get_config(PCA9552State *s, int pin)
>>>>    {
>>>>        uint8_t reg   = PCA9552_LS0 + (pin / 4);
>>>> @@ -169,6 +173,84 @@ static int pca9552_event(I2CSlave *i2c, enum i2c_event event)
>>>>        return 0;
>>>>    }
>>>>    +static void pca9552_get_led(Object *obj, Visitor *v, const char *name,
>>>> +                            void *opaque, Error **errp)
>>>> +{
>>>> +    PCA9552State *s = PCA9552(obj);
>>>> +    int led, rc, reg;
>>>> +    char *str;
>>>> +    uint8_t state;
>>>> +
>>>> +    rc = sscanf(name, "led%2d", &led);
>>>> +    if (rc != 1) {
>>>> +        error_setg(errp, "%s: error reading %s", __func__, name);
>>>> +        return;
>>>> +    }
>>>> +    if (led < 0 || led > s->nr_leds) {
>>>> +        error_setg(errp, "%s invalid led %s", __func__, name);
>>>> +        return;
>>>> +    }
>>>> +    /*
>>>> +     * Get the LSx register as the qom interface should expose the device
>>>> +     * state, not the modeled 'input line' behaviour which would come from
>>>> +     * reading the INPUTx reg
>>>> +     */
>>>> +    reg = PCA9552_LS0 + led / 4;
>>>> +    state = (pca9552_read(s, reg) >> (led % 8)) & 0x3;
>>>
>>> Could we add accessors to extract the register fields and to clarify
>>> the layout ?
>>>
>>>> +    str = g_strdup(led_state[state]);
>>>> +    visit_type_str(v, name, &str, errp);
>>>> +}
>>>> +
>>>> +/*
>>>> + * Return an LED selector register value based on an existing one, with
>>>> + * the appropriate 2-bit state value set for the given LED number (0-3).
>>>> + */
>>>> +static inline uint8_t pca955x_ledsel(uint8_t oldval, int led_num, int state)
>>>> +{
>>>> +        return (oldval & (~(0x3 << (led_num << 1)))) |
>>>> +                ((state & 0x3) << (led_num << 1));
>>>> +}
>>>> +
>>>> +static void pca9552_set_led(Object *obj, Visitor *v, const char *name,
>>>> +                            void *opaque, Error **errp)
>>>> +{
>>>> +    PCA9552State *s = PCA9552(obj);
>>>> +    Error *local_err = NULL;
>>>> +    int led, rc, reg, val;
>>>> +    uint8_t state;
>>>> +    char *state_str;
>>>> +
>>>> +    visit_type_str(v, name, &state_str, &local_err);
>>>> +    if (local_err) {
>>>> +        error_propagate(errp, local_err);
>>>> +        return;
>>>> +    }
>>>> +    rc = sscanf(name, "led%2d", &led);
>>>> +    if (rc != 1) {
>>>> +        error_setg(errp, "%s: error reading %s", __func__, name);
>>>> +        return;
>>>> +    }
>>>> +    if (led < 0 || led > s->nr_leds) {
>>>> +        error_setg(errp, "%s invalid led %s", __func__, name);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    for (state = 0; state < ARRAY_SIZE(led_state); state++) {
>>>> +        if (!strcmp(state_str, led_state[state])) {
>>>> +            break;
>>>> +        }
>>>> +    }
>>>> +    if (state >= ARRAY_SIZE(led_state)) {
>>>> +        error_setg(errp, "%s invalid led state %s", __func__, state_str);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    reg = PCA9552_LS0 + led / 4;
>>>> +    val = pca9552_read(s, reg);
>>>> +    val = pca955x_ledsel(val, led % 4, state);
>>>> +    pca9552_write(s, reg, val);
>>>> +}
>>>> +
>>>>    static const VMStateDescription pca9552_vmstate = {
>>>>        .name = "PCA9552",
>>>>        .version_id = 0,
>>>> @@ -204,6 +286,7 @@ static void pca9552_reset(DeviceState *dev)
>>>>    static void pca9552_initfn(Object *obj)
>>>>    {
>>>>        PCA9552State *s = PCA9552(obj);
>>>> +    int led;
>>>>          /* If support for the other PCA955X devices are implemented, these
>>>>         * constant values might be part of class structure describing the
>>>> @@ -211,6 +294,14 @@ static void pca9552_initfn(Object *obj)
>>>>         */
>>>>        s->max_reg = PCA9552_LS3;
>>>>        s->nr_leds = 16;
>>>> +
>>>> +    for (led = 0; led < s->nr_leds; led++) {
>>>> +        char *name;
>>>> +
>>>> +        name = g_strdup_printf("led%d", led);
>>>> +        object_property_add(obj, name, "bool", pca9552_get_led, pca9552_set_led,
>>>> +                            NULL, NULL, NULL);
>>>
>>> It misses a :
>>>
>>>      g_free(name)
>>>
>>> C.
>>>
>>>> +    }
>>>>    }
>>>>      static void pca9552_class_init(ObjectClass *klass, void *data)
>>>>
>>>
>>>
>>
>