Messages in this thread | | | Subject | Re: [For Linux 4/4] xen/displif: add ABI for para-virtual display | From | Julien Grall <> | Date | Fri, 7 Apr 2017 14:50:57 +0100 |
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Hi Oleksandr,
On 07/04/17 09:30, Oleksandr Andrushchenko wrote: > +/* > + ****************************************************************************** > + * Back to front events delivery > + ****************************************************************************** > + * In order to deliver asynchronous events from back to front a shared page is > + * allocated by front and its granted reference propagated to back via > + * XenStore entries (evt-ring-ref/evt-event-channel). > + * This page has a common header used by both front and back to synchronize > + * access and control event's ring buffer, while back being a producer of the > + * events and front being a consumer. The rest of the page after the header > + * is used for event packets. > + * > + * Upon reception of an event(s) front may confirm its reception > + * for either each event, group of events or none. > + */ > + > +struct xendispl_event_page { > + uint32_t in_cons; > + uint32_t in_prod; > + uint8_t reserved[56]; > +}; > + > +#define XENDISPL_EVENT_PAGE_SIZE 4096
This will be always the size of a grant (e.g xen page size), right? If so, I would prefer if you use XEN_PAGE_SIZE to so we can easily update Linux in the case Xen is using a different page size.
Note that the Front-end, Backend and Xen may use different page size, so your drivers would need to cope with that. The current approach is to always use the page granularity of Xen.
> +#define XENDISPL_IN_RING_OFFS (sizeof(struct xendispl_event_page)) > +#define XENDISPL_IN_RING_SIZE (XENDISPL_EVENT_PAGE_SIZE - XENDISPL_IN_RING_OFFS) > +#define XENDISPL_IN_RING_LEN (XENDISPL_IN_RING_SIZE / sizeof(struct xendispl_evt)) > +#define XENDISPL_IN_RING(page) \ > + ((struct xendispl_evt *)((char *)(page) + XENDISPL_IN_RING_OFFS)) > +#define XENDISPL_IN_RING_REF(page, idx) \ > + (XENDISPL_IN_RING((page))[(idx) % XENDISPL_IN_RING_LEN]) > + > +#endif /* __XEN_PUBLIC_IO_DISPLIF_H__ */ > + > +/* > + * Local variables: > + * mode: C > + * c-file-style: "BSD" > + * c-basic-offset: 4 > + * tab-width: 4 > + * indent-tabs-mode: nil > + * End: > + */ >
Cheers,
-- Julien Grall
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