Re: [PATCH 1/2] ubi: mount partitions specified in device tree

[Daniel Golle <daniel@makrotopia.org>]

Hi!

I got some remarks here:

On Sat, Jun 18, 2016 at 09:17:55PM +0200, Hauke Mehrtens wrote:
> This makes it possible to open a ubi layer in device tree, this is
> helpful when the rootfs is on a ubi layer. It loops though all mtd
> partitions and mounts the partition which is compatible with
> "ubi,volume". The same was only possible with kernel command line
> arguments before.

Strictly speaking this doesn't describe what this change does.
Rather than mounting anything you are creating ubiblock devices...

More comments in-line.

> 
> Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
> ---
>  Documentation/devicetree/bindings/mtd/ubi.txt | 33 ++++++++++++++
>  drivers/mtd/ubi/block.c                       | 63 +++++++++++++++++++++++++++
>  2 files changed, 96 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/ubi.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/ubi.txt b/Documentation/devicetree/bindings/mtd/ubi.txt
> new file mode 100644
> index 0000000..5fcd47e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/ubi.txt
> @@ -0,0 +1,33 @@
> +UBI - Unsorted block images
> +
> +Describe of a UBI layer in device tree.
> +
> + - compatible:		"ubi,device", This marks a partition that contains
> + 			a ubi layer.
> + - vid_hdr_offs:	Optional parameter specifies UBI VID header position
> + 			to be used by UBI. (default value if 0)
> + - max_beb_per1024:	Optional parameter specifies the maximum expected bad
> + 			eraseblock per 1024 eraseblocks.
> + 			(default value CONFIG_MTD_UBI_BEB_LIMIT)
> + -ubi_num:		Optional parameter specifies UBI device number
> + 			which have to be assigned to the newly created UBI
> + 			device (assigned automatically by default)
> +
> +Example:
> +
> +partitions {
> +	compatible = "fixed-partitions";
> +	#address-cells = <1>;
> +	#size-cells = <1>;
> +
> +	partition@0 {
> +		label = "uboot";
> +		reg = <0x00000 0x100000>;
> +	};
> +
> +	partition@1c0000 {
> +		label = "system_sw";
> +		reg = <0x1c0000 0xc800000>;
> +		compatible = "ubi,device";
> +	};
> +};

Similar to the other patch, the example in the documentation is
swapped and doesn't match with the code added by the patch.



> diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
> index ebf46ad..5ed390d 100644
> --- a/drivers/mtd/ubi/block.c
> +++ b/drivers/mtd/ubi/block.c

Wait a moment: What about ubifs being the root filesystem? That
doesn't need a ubiblock device to be created...


> @@ -1,6 +1,7 @@
>  /*
>   * Copyright (c) 2014 Ezequiel Garcia
>   * Copyright (c) 2011 Free Electrons
> + * Copyright (c) 2016 Hauke Mehrtens <hauke@hauke-m.de>
>   *
>   * Driver parameter handling strongly based on drivers/mtd/ubi/build.c
>   *   Copyright (c) International Business Machines Corp., 2006
> @@ -41,6 +42,7 @@
>  #include <linux/kernel.h>
>  #include <linux/list.h>
>  #include <linux/mutex.h>
> +#include <linux/of.h>
>  #include <linux/slab.h>
>  #include <linux/mtd/ubi.h>
>  #include <linux/workqueue.h>
> @@ -628,6 +630,64 @@ static void __init ubiblock_create_from_param(void)
>  	}
>  }
>  
> +static void __init ubiblock_create_from_device_tree(void)
> +{
> +	int ubi_num;
> +	const char *name;
> +	u32 mode;
> +	struct ubi_device *ubi;
> +	struct ubi_volume_desc *desc;
> +	struct ubi_volume_info vi;
> +	struct mtd_info *mtd;
> +	struct device_node *volume;
> +	int ret;
> +
> +	for (ubi_num = 0; ubi_num < UBI_MAX_DEVICES; ubi_num++) {
> +		ubi = ubi_get_device(ubi_num);
> +		if (!ubi)
> +			continue;
> +		mtd = ubi->mtd;
> +		if (!mtd || !of_device_is_compatible(mtd->dev.of_node,
> +						     "ubi,device")) {
> +			ubi_put_device(ubi);
> +			continue;
> +		}
> +
> +		for_each_child_of_node(mtd->dev.of_node, volume) {
> +			if (!of_device_is_compatible(volume, "ubi,volume"))
> +				continue;
> +
> +			ret = of_property_read_string(volume, "name", &name);
> +			if (ret)
> +				continue;
> +
> +			ret = of_property_read_u32(volume, "ubi-mode", &mode);
> +			if (ret)
> +				continue;
> +
> +			desc = ubi_open_volume_nm(ubi_num, name, mode);
> +			if (IS_ERR(desc)) {
> +				pr_err(
> +				       "UBI: block: can't open volume %s on ubi%d, err=%ld",
> +				       name, ubi_num, PTR_ERR(desc));
> +				continue;
> +			}
> +
> +			ubi_get_volume_info(desc, &vi);
> +			ubi_close_volume(desc);
> +
> +			ret = ubiblock_create(&vi);
> +			if (ret) {
> +				pr_err(
> +				       "UBI: block: can't add '%s' volume on ubi%d, err=%d",
> +				       vi.name, ubi_num, ret);
> +				continue;
> +			}
> +		}
> +		ubi_put_device(ubi);
> +	}
> +}
> +
>  static void ubiblock_remove_all(void)
>  {
>  	struct ubiblock *next;
> @@ -658,6 +718,9 @@ int __init ubiblock_init(void)
>  	 */
>  	ubiblock_create_from_param();
>  
> +	/* Attach block devices from device tree */
> +	ubiblock_create_from_device_tree();
> +

Probably you also want to set ROOT_DEV similar to what we currently
do in

https://git.lede-project.org/?p=source.git;a=blob;f=target/linux/generic/patches-4.4/493-ubi-set-ROOT_DEV-to-ubiblock-rootfs-if-unset.patch

>  	/*
>  	 * Block devices are only created upon user requests, so we ignore
>  	 * existing volumes.
> -- 
> 2.8.1
> 
> 
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