Module parameter support for Rust modules was merged a few releases back.
Add module parameter support to the rnull driver.

This allows the user to control the driver either via configfs or module
parameters, just like the C counterpart.

Please note that the rust module parameters do not support boolean values.
Flags that should have been booleans are parsed as integers and compared to
zero.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 drivers/block/rnull/rnull.rs | 51 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index 2c83b014b05e9..bd883a5061cab 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -19,11 +19,13 @@
         },
     },
     error::Result,
-    pr_info,
+    new_mutex, pr_info,
     prelude::*,
+    str::CString,
     sync::{
         aref::ARef,
-        Arc, //
+        Arc,
+        Mutex, //
     },
 };
 use pin_init::PinInit;
@@ -34,20 +36,65 @@
     authors: ["Andreas Hindborg"],
     description: "Rust implementation of the C null block driver",
     license: "GPL v2",
+    params: {
+        gb: u64 {
+            default: 4,
+            description: "Device capacity in GiB",
+        },
+        rotational: u8 {
+            default: 0,
+            description:
+            "Set the rotational feature for the device (0 for false, 1 for true). Default: 0",
+        },
+        bs: u32 {
+            default: 4096,
+            description: "Block size (in bytes)",
+        },
+        nr_devices: u64 {
+            default: 1,
+            description: "Number of devices to register",
+        },
+        irqmode: u8 {
+            default: 0,
+            description:  "IRQ completion handler. 0-none, 1-softirq",
+        },
+    },
 }
 
 #[pin_data]
 struct NullBlkModule {
     #[pin]
     configfs_subsystem: kernel::configfs::Subsystem<configfs::Config>,
+    #[pin]
+    param_disks: Mutex<KVec<GenDisk<NullBlkDevice>>>,
 }
 
 impl kernel::InPlaceModule for NullBlkModule {
     fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
         pr_info!("Rust null_blk loaded\n");
 
+        let mut disks = KVec::new();
+
+        let defer_init = move || -> Result<_, Error> {
+            for i in 0..(*module_parameters::nr_devices.value()) {
+                let name = CString::try_from_fmt(fmt!("rnullb{}", i))?;
+
+                let disk = NullBlkDevice::new(
+                    &name,
+                    *module_parameters::bs.value(),
+                    *module_parameters::rotational.value() != 0,
+                    *module_parameters::gb.value() * 1024,
+                    (*module_parameters::irqmode.value()).try_into()?,
+                )?;
+                disks.push(disk, GFP_KERNEL)?;
+            }
+
+            Ok(disks)
+        };
+
         try_pin_init!(Self {
             configfs_subsystem <- configfs::subsystem(),
+            param_disks <- new_mutex!(defer_init()?),
         })
     }
 }

-- 
2.51.2