Peter Maydell <peter.mayd...@linaro.org> writes:
> For the IoTKit MPC support, we need to wire together the
> interrupt outputs of 17 MPCs; this exceeds the current
> value of MAX_OR_LINES. Increase MAX_OR_LINES to 32 (which
> should be enough for anyone).
>
> The tricky part is retaining the migration compatibility for
> existing OR gates; we add a subsection which is only used
> for larger OR gates, and define it such that we can freely
> increase MAX_OR_LINES in future (or even move to a dynamically
> allocated levels[] array without an upper size limit) without
> breaking compatibility.
>
> Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Reviewed-by: Alex Bennée <alex.ben...@linaro.org>
> ---
> include/hw/or-irq.h | 5 ++++-
> hw/core/or-irq.c | 39 +++++++++++++++++++++++++++++++++++++--
> 2 files changed, 41 insertions(+), 3 deletions(-)
>
> diff --git a/include/hw/or-irq.h b/include/hw/or-irq.h
> index 3f6fc1b58a4..5a31e5a1881 100644
> --- a/include/hw/or-irq.h
> +++ b/include/hw/or-irq.h
> @@ -31,7 +31,10 @@
>
> #define TYPE_OR_IRQ "or-irq"
>
> -#define MAX_OR_LINES 16
> +/* This can safely be increased if necessary without breaking
> + * migration compatibility (as long as it remains greater than 15).
> + */
> +#define MAX_OR_LINES 32
>
> typedef struct OrIRQState qemu_or_irq;
>
> diff --git a/hw/core/or-irq.c b/hw/core/or-irq.c
> index f9d76c46415..a86901b673c 100644
> --- a/hw/core/or-irq.c
> +++ b/hw/core/or-irq.c
> @@ -66,14 +66,49 @@ static void or_irq_init(Object *obj)
> qdev_init_gpio_out(DEVICE(obj), &s->out_irq, 1);
> }
>
> +/* The original version of this device had a fixed 16 entries in its
> + * VMState array; devices with more inputs than this need to
> + * migrate the extra lines via a subsection.
> + * The subsection migrates as much of the levels[] array as is needed
> + * (including repeating the first 16 elements), to avoid the awkwardness
> + * of splitting it in two to meet the requirements of VMSTATE_VARRAY_UINT16.
> + */
> +#define OLD_MAX_OR_LINES 16
> +#if MAX_OR_LINES < OLD_MAX_OR_LINES
> +#error MAX_OR_LINES must be at least 16 for migration compatibility
> +#endif
> +
> +static bool vmstate_extras_needed(void *opaque)
> +{
> + qemu_or_irq *s = OR_IRQ(opaque);
> +
> + return s->num_lines >= OLD_MAX_OR_LINES;
> +}
> +
> +static const VMStateDescription vmstate_or_irq_extras = {
> + .name = "or-irq-extras",
> + .version_id = 1,
> + .minimum_version_id = 1,
> + .needed = vmstate_extras_needed,
> + .fields = (VMStateField[]) {
> + VMSTATE_VARRAY_UINT16_UNSAFE(levels, qemu_or_irq, num_lines, 0,
> + vmstate_info_bool, bool),
> + VMSTATE_END_OF_LIST(),
> + },
> +};
> +
> static const VMStateDescription vmstate_or_irq = {
> .name = TYPE_OR_IRQ,
> .version_id = 1,
> .minimum_version_id = 1,
> .fields = (VMStateField[]) {
> - VMSTATE_BOOL_ARRAY(levels, qemu_or_irq, MAX_OR_LINES),
> + VMSTATE_BOOL_SUB_ARRAY(levels, qemu_or_irq, 0, OLD_MAX_OR_LINES),
> VMSTATE_END_OF_LIST(),
> - }
> + },
> + .subsections = (const VMStateDescription*[]) {
> + &vmstate_or_irq_extras,
> + NULL
> + },
> };
>
> static Property or_irq_properties[] = {
--
Alex Bennée
