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dev: implement reading from block devices

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reading from block devices is done using the block cache (bcache).
This cache stores sectors from a block device in pages of memory
marked as 'cached', which will allow them to be reclaimed when
memory pressure is high (TODO).

while block device drivers implement callbacks allowing reading/writing
at block-granularity, the device subsystem uses the block cache to
implement reading/writing at byte-granularity in a driver-agnostic way.

block drivers can disable the block cache for their devices, but this
will require that any clients communicate with the devices at
block-granularity.

also added an offset parameter to device and object read/write functions/callbacks.
This commit is contained in:
max 🍓
2023-07-09 21:58:40 +01:00
parent 53440653f2
commit 3233169f25
14 changed files with 435 additions and 52 deletions
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22
init/main.c
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@@ -29,7 +29,7 @@ void print_kernel_banner(void)
static void hang(void)
{
while (1) {
printk("tick");
//printk("tick");
milli_sleep(2000);
}
}
@@ -110,5 +110,25 @@ void kernel_init(uintptr_t arg)
tty_connect_foreground_input_device(cast_to_device(kbd));
}
struct object *disk;
status = object_get("/dev/block/disk0", &disk);
if (status == KERN_OK) {
unsigned char buf[32] = {0};
struct device *disk_dev = cast_to_device(disk);
size_t nread = 0;
status = device_read(disk_dev, buf, 1, 32, &nread, 0);
if (status == KERN_OK) {
printk("read %zu bytes from /dev/block/disk0:", nread);
for (int i = 0; i < sizeof buf; i++) {
printk("%02xh", buf[i]);
}
} else {
printk("failed to read from block device (%s)", kern_status_string(status));
}
} else {
printk("cannot open block device (%s)", kern_status_string(status));
}
hang();
}