[Minios-devel] [UNIKRAFT PATCH v2 11/16] plat/xen/drivers/blk: Read device capabilities

[Roxana Nicolescu <nicolescu.roxana1996@xxxxxxxxx>]

This patch introduces the function which reads the capabilities
from Xenstore, after connection to backend.

Signed-off-by: Roxana Nicolescu <nicolescu.roxana1996@xxxxxxxxx>
---
 plat/xen/drivers/blk/blkfront_xs.c | 43 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/plat/xen/drivers/blk/blkfront_xs.c 
b/plat/xen/drivers/blk/blkfront_xs.c
index 86aee13b..d7d5ee94 100644
--- a/plat/xen/drivers/blk/blkfront_xs.c
+++ b/plat/xen/drivers/blk/blkfront_xs.c
@@ -164,6 +164,43 @@ out:
        return err;
 }
 
+/*
+ * Get device capabilities (sector_size, etc)
+ * from the backend after it switched to Connected State.
+ */
+static int blkfront_xb_get_capabilities(struct blkfront_dev *blkdev)
+{
+       struct xenbus_device *xendev;
+       char *mode;
+       int err = 0;
+
+       UK_ASSERT(blkdev != NULL);
+       xendev = blkdev->xendev;
+       err = xs_scanf(XBT_NIL, xendev->otherend, "sectors",
+               "%lu", &blkdev->blkdev.capabilities.sectors);
+       if (err < 0) {
+               uk_pr_err("Failed to read nb_sectors from xs: %d\n", err);
+               return err;
+       }
+
+       err = xs_scanf(XBT_NIL, xendev->otherend, "sector-size",
+                       "%lu", &blkdev->blkdev.capabilities.ssize);
+       if (err < 0) {
+               uk_pr_err("Failed to read ssize from xs: %d\n", err);
+               return err;
+       }
+
+       mode = xs_read(XBT_NIL, xendev->otherend, "mode");
+       if (PTRISERR(mode)) {
+               uk_pr_err("Failed to read mode from xs: %d.\n", err);
+               return PTR2ERR(mode);
+       }
+
+       blkdev->blkdev.capabilities.mode = (*mode == 'r') ? O_RDONLY : O_RDWR;
+
+       free(mode);
+       return 0;
+}
 
 /* Write info for a specific queue in xenstore.
  * If there is only one queue, the path does not
@@ -451,6 +488,12 @@ int blkfront_xb_connect(struct blkfront_dev *blkdev)
        if (err)
                goto err;
 
+       err = blkfront_xb_get_capabilities(blkdev);
+       if (err) {
+               uk_pr_err("Failed to extract info from backend: %d.\n", err);
+               goto err;
+       }
+
 err:
        return err;
 }
-- 
2.11.0


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