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Subject: Re: [PATCH 2/9] drm/xen-front: Implement Xen bus state handling
To:     Juergen Gross <jgross@suse.com>,
        Oleksandr Andrushchenko <andr2000@gmail.com>,
        xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
        dri-devel@lists.freedesktop.org, airlied@linux.ie,
        daniel.vetter@intel.com, seanpaul@chromium.org,
        gustavo@padovan.org, boris.ostrovsky@oracle.com,
        konrad.wilk@oracle.com
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From:   Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>
Message-ID: <ca79a556-54bc-4ea7-e708-614269b11d5b@epam.com>
Date:   Wed, 21 Feb 2018 10:50:01 +0200
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On 02/21/2018 10:23 AM, Juergen Gross wrote:
> On 21/02/18 09:03, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> Initial handling for Xen bus states: implement
>> Xen bus state machine for the frontend driver according to
>> the state diagram and recovery flow from display para-virtualized
>> protocol: xen/interface/io/displif.h.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   drivers/gpu/drm/xen/xen_drm_front.c | 124 +++++++++++++++++++++++++++++++++++-
>>   drivers/gpu/drm/xen/xen_drm_front.h |  26 ++++++++
>>   2 files changed, 149 insertions(+), 1 deletion(-)
>>   create mode 100644 drivers/gpu/drm/xen/xen_drm_front.h
>>
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
>> index fd372fb464a1..d0306f9d660d 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front.c
>> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
>> @@ -24,19 +24,141 @@
>>   
>>   #include <xen/interface/io/displif.h>
>>   
>> +#include "xen_drm_front.h"
>> +
>> +static void xen_drv_remove_internal(struct xen_drm_front_info *front_info)
>> +{
>> +}
>> +
>> +static int backend_on_initwait(struct xen_drm_front_info *front_info)
>> +{
>> +	return 0;
>> +}
>> +
>> +static int backend_on_connected(struct xen_drm_front_info *front_info)
>> +{
>> +	return 0;
>> +}
>> +
>> +static void backend_on_disconnected(struct xen_drm_front_info *front_info)
>> +{
>> +	xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
>> +}
>> +
>>   static void backend_on_changed(struct xenbus_device *xb_dev,
>>   		enum xenbus_state backend_state)
>>   {
>> +	struct xen_drm_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
>> +	int ret;
>> +
>> +	DRM_DEBUG("Backend state is %s, front is %s\n",
>> +			xenbus_strstate(backend_state),
>> +			xenbus_strstate(xb_dev->state));
>> +
>> +	switch (backend_state) {
>> +	case XenbusStateReconfiguring:
>> +		/* fall through */
>> +	case XenbusStateReconfigured:
>> +		/* fall through */
>> +	case XenbusStateInitialised:
>> +		break;
>> +
>> +	case XenbusStateInitialising:
>> +		/* recovering after backend unexpected closure */
>> +		backend_on_disconnected(front_info);
>> +		break;
>> +
>> +	case XenbusStateInitWait:
>> +		/* recovering after backend unexpected closure */
>> +		backend_on_disconnected(front_info);
>> +		if (xb_dev->state != XenbusStateInitialising)
>> +			break;
>> +
>> +		ret = backend_on_initwait(front_info);
>> +		if (ret < 0)
>> +			xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
>> +		else
>> +			xenbus_switch_state(xb_dev, XenbusStateInitialised);
>> +		break;
>> +
>> +	case XenbusStateConnected:
>> +		if (xb_dev->state != XenbusStateInitialised)
>> +			break;
>> +
>> +		ret = backend_on_connected(front_info);
>> +		if (ret < 0)
>> +			xenbus_dev_fatal(xb_dev, ret, "initializing DRM driver");
>> +		else
>> +			xenbus_switch_state(xb_dev, XenbusStateConnected);
>> +		break;
>> +
>> +	case XenbusStateClosing:
>> +		/*
>> +		 * in this state backend starts freeing resources,
>> +		 * so let it go into closed state, so we can also
>> +		 * remove ours
>> +		 */
>> +		break;
>> +
>> +	case XenbusStateUnknown:
>> +		/* fall through */
>> +	case XenbusStateClosed:
>> +		if (xb_dev->state == XenbusStateClosed)
>> +			break;
>> +
>> +		backend_on_disconnected(front_info);
>> +		break;
>> +	}
>>   }
>>   
>>   static int xen_drv_probe(struct xenbus_device *xb_dev,
>>   		const struct xenbus_device_id *id)
>>   {
>> -	return 0;
>> +	struct xen_drm_front_info *front_info;
>> +
>> +	front_info = devm_kzalloc(&xb_dev->dev,
>> +			sizeof(*front_info), GFP_KERNEL);
>> +	if (!front_info) {
>> +		xenbus_dev_fatal(xb_dev, -ENOMEM, "allocating device memory");
> No need for message in case of allocation failure: this is
> handled in memory allocation already.
Will remove, thank you
>
> Juergen