dri2: Add DRI2GetParam request (v2)

Bump dri2proto dependency to 2.7.
Bump DRI2INFOREC_VERSION to 7.

This new protocol request effectively allows clients to perform feature
detection on the DDX. The request was added in DRI2 protocol 1.4.

If I had DRI2GetParam in June 2011, when I was implementing support in the
Intel DDX and Mesa for new hardware that required a new DRI2 attachment
format, then I could have avoided a week of pain caused by the necessity
to write a horrid feature detection hack [1] in Mesa. In the future, when
the work begins to add MSAA support to the Intel DDX, having a clean way
to do feature detection will allow us to avoid revisiting and expanding
that hack.

[1] mesa, commit aea2236a, function intel_verify_dri2_has_hiz

v2: If driver doesn't define ds->GetParam, dont' crash. Fall back to
    default behavior, per keithp.

Reviewed-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Eric Anholt <eric@anholt.net> (v1)
Reviewed-by: Ian Romanick <idr@freedesktop.org> (v1)
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>

configure.ac

@@ -773,7 +773,7 @@ RECORDPROTO="recordproto >= 1.13.99.1"
 SCRNSAVERPROTO="scrnsaverproto >= 1.1"
 RESOURCEPROTO="resourceproto >= 1.2.0"
 DRIPROTO="xf86driproto >= 2.1.0"
-DRI2PROTO="dri2proto >= 2.6"
+DRI2PROTO="dri2proto >= 2.7"
 XINERAMAPROTO="xineramaproto"
 BIGFONTPROTO="xf86bigfontproto >= 1.2.0"
 DGAPROTO="xf86dgaproto >= 2.0.99.1"

hw/xfree86/dri2/dri2.c

@@ -107,6 +107,7 @@ typedef struct _DRI2Screen {
     DRI2AuthMagicProcPtr AuthMagic;
     DRI2ReuseBufferNotifyProcPtr ReuseBufferNotify;
     DRI2SwapLimitValidateProcPtr SwapLimitValidate;
+    DRI2GetParamProcPtr GetParam;
 
     HandleExposuresProcPtr HandleExposures;
 
@@ -1210,6 +1211,11 @@ DRI2ScreenInit(ScreenPtr pScreen, DRI2InfoPtr info)
         ds->SwapLimitValidate = info->SwapLimitValidate;
     }
 
+    if (info->version >= 7) {
+        ds->GetParam = info->GetParam;
+        cur_minor = 4;
+    }
+
     /*
      * if the driver doesn't provide an AuthMagic function or the info struct
      * version is too low, it relies on the old method (using libdrm) or fail
@@ -1332,3 +1338,38 @@ DRI2Version(int *major, int *minor)
     if (minor != NULL)
         *minor = DRI2VersRec.minorversion;
 }
+
+int
+DRI2GetParam(ClientPtr client,
+             DrawablePtr drawable,
+             CARD64 param,
+             BOOL *is_param_recognized,
+             CARD64 *value)
+{
+    DRI2ScreenPtr ds = DRI2GetScreen(drawable->pScreen);
+    char high_byte = (param >> 24);
+
+    switch (high_byte) {
+    case 0:
+        /* Parameter names whose high_byte is 0 are reserved for the X
+         * server. The server currently recognizes no parameters.
+         */
+        goto not_recognized;
+    case 1:
+        /* Parameter names whose high byte is 1 are reserved for the DDX. */
+        if (ds->GetParam)
+            return ds->GetParam(client, drawable, param,
+                                is_param_recognized, value);
+        else
+            goto not_recognized;
+    default:
+        /* Other parameter names are reserved for future use. They are never
+         * recognized.
+         */
+        goto not_recognized;
+    }
+
+not_recognized:
+    *is_param_recognized = FALSE;
+    return Success;
+}

hw/xfree86/dri2/dri2.h

@@ -175,10 +175,24 @@ typedef void (*DRI2InvalidateProcPtr) (DrawablePtr pDraw, void *data, XID id);
 typedef Bool (*DRI2SwapLimitValidateProcPtr) (DrawablePtr pDraw,
                                               int swap_limit);
 
+/**
+ * \brief Get the value of a parameter.
+ *
+ * The parameter's \a value is looked up on the screen associated with
+ * \a pDrawable.
+ *
+ * \return \c Success or error code.
+ */
+typedef int (*DRI2GetParamProcPtr) (ClientPtr client,
+                                    DrawablePtr pDrawable,
+                                    CARD64 param,
+                                    BOOL *is_param_recognized,
+                                    CARD64 *value);
+
 /**
  * Version of the DRI2InfoRec structure defined in this header
  */
-#define DRI2INFOREC_VERSION 6
+#define DRI2INFOREC_VERSION 7
 
 typedef struct {
     unsigned int version;       /**< Version of this struct */
@@ -211,6 +225,10 @@ typedef struct {
 
     DRI2ReuseBufferNotifyProcPtr ReuseBufferNotify;
     DRI2SwapLimitValidateProcPtr SwapLimitValidate;
+
+    /* added in version 7 */
+
+    DRI2GetParamProcPtr GetParam;
 } DRI2InfoRec, *DRI2InfoPtr;
 
 extern _X_EXPORT int DRI2EventBase;
@@ -308,4 +326,10 @@ extern _X_EXPORT void DRI2WaitMSCComplete(ClientPtr client, DrawablePtr pDraw,
                                           int frame, unsigned int tv_sec,
                                           unsigned int tv_usec);
 
+extern _X_EXPORT int DRI2GetParam(ClientPtr client,
+                                  DrawablePtr pDrawable,
+                                  CARD64 param,
+                                  BOOL *is_param_recognized,
+                                  CARD64 *value);
+
 #endif

hw/xfree86/dri2/dri2ext.c

@@ -534,6 +534,37 @@ ProcDRI2WaitSBC(ClientPtr client)
     return status;
 }
 
+static int
+ProcDRI2GetParam(ClientPtr client)
+{
+    REQUEST(xDRI2GetParamReq);
+    xDRI2GetParamReply rep;
+    DrawablePtr pDrawable;
+    CARD64 value;
+    int status;
+
+    REQUEST_SIZE_MATCH(xDRI2GetParamReq);
+    rep.type = X_Reply;
+    rep.length = 0;
+    rep.sequenceNumber = client->sequence;
+
+    if (!validDrawable(client, stuff->drawable, DixReadAccess,
+                       &pDrawable, &status))
+        return status;
+
+    status = DRI2GetParam(client, pDrawable, stuff->param,
+                          &rep.is_param_recognized, &value);
+    rep.value_hi = value >> 32;
+    rep.value_lo = value & 0xffffffff;
+
+    if (status != Success)
+        return status;
+
+    WriteToClient(client, sizeof(xDRI2GetParamReply), &rep);
+
+    return status;
+}
+
 static int
 ProcDRI2Dispatch(ClientPtr client)
 {
@@ -572,6 +603,8 @@ ProcDRI2Dispatch(ClientPtr client)
         return ProcDRI2WaitSBC(client);
     case X_DRI2SwapInterval:
         return ProcDRI2SwapInterval(client);
+    case X_DRI2GetParam:
+        return ProcDRI2GetParam(client);
     default:
         return BadRequest;
     }