On Tue, 2014-08-05 at 21:08 +0100, Chris Metcalf wrote:
> >> In addition, we also have user binaries
> >> in the wild that know to look for /sys/devices/platform/srom/ paths,
> >> so I'm pretty reluctant to change this path without good reason.
> > So what is the srom class for then if not for device discovery? And why
> > do they look for them in the first place? To get relevant character
> > device's data, if I understand it right?
> >
> > Maybe you could just register a simple "proper" platform device for all
> > the sroms and then hang the class devices from it? I can type some code
> > doing this if it sound reasonably?
>
> I'm not sure exactly what you mean by device discovery here.
> The
> subdirectories under /sys/devices/platform/srom/ correspond to partitions
> in the SPI-ROM, which are software constructs created by the Tilera hypervisor.
> By default we have three, where the first holds boot data that the chip
> can use to boot out of hardware, and the other two are smaller partitions
> for boot- and user-specific data. We use the /sys files primarily to get the
> page size and sector size for the sroms, and also export other interesting
> information like the total size of the particular srom device.
>
> Thank you for volunteering to write a bit of code; if that's the best
> way to clarify this for us, fantastic, or else pointing us at existing
> good practices or documentation would be great too.
I was thinking about something like the following (warning, untested)
8<-------------------------------------------
>From c53f0a2492d6cd38d1f82d57916a6528b071e8a8 Mon Sep 17 00:00:00 2001
From: Pawel Moll <pawel.moll@xxxxxxx>
Date: Fri, 8 Aug 2014 16:32:58 +0100
Subject: [PATCH] char: tile-srom: Add real platform bus parent
Add a real platform bus device as a parent for
the srom class devices, to prevent non-platform
devices hanging from the bus root.
Signed-off-by: Pawel Moll <pawel.moll@xxxxxxx>
---
drivers/char/tile-srom.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/char/tile-srom.c b/drivers/char/tile-srom.c
index bd37747..7fb0fd5 100644
--- a/drivers/char/tile-srom.c
+++ b/drivers/char/tile-srom.c
@@ -76,6 +76,7 @@ MODULE_LICENSE("GPL");
static int srom_devs; /* Number of SROM partitions */
static struct cdev srom_cdev;
+static struct platform_device *srom_parent;
static struct class *srom_class;
static struct srom_dev *srom_devices;
@@ -350,7 +351,7 @@ static int srom_setup_minor(struct srom_dev *srom, int index)
SROM_PAGE_SIZE_OFF, sizeof(srom->page_size)) < 0)
return -EIO;
- dev = device_create(srom_class, &platform_bus,
+ dev = device_create(srom_class, srom_parent,
MKDEV(srom_major, index), srom, "%d", index);
return PTR_ERR_OR_ZERO(dev);
}
@@ -415,6 +416,13 @@ static int srom_init(void)
if (result < 0)
goto fail_chrdev;
+ /* Create a parent device */
+ srom_parent = platform_device_register_simple("srom", -1, NULL, 0);
+ if (IS_ERR(srom_parent)) {
+ result = PTR_ERR(srom_parent);
+ goto fail_pdev;
+ }
+
/* Create a sysfs class. */
srom_class = class_create(THIS_MODULE, "srom");
if (IS_ERR(srom_class)) {
@@ -438,6 +446,8 @@ fail_class:
device_destroy(srom_class, MKDEV(srom_major, i));
class_destroy(srom_class);
fail_cdev:
+ platform_device_unregister(srom_parent);
+fail_pdev:
cdev_del(&srom_cdev);
fail_chrdev:
unregister_chrdev_region(dev, srom_devs);
@@ -454,6 +464,7 @@ static void srom_cleanup(void)
device_destroy(srom_class, MKDEV(srom_major, i));
class_destroy(srom_class);
cdev_del(&srom_cdev);
+ platform_device_unregister(srom_parent);
unregister_chrdev_region(MKDEV(srom_major, 0), srom_devs);
kfree(srom_devices);
}
--
1.9.1
8<-------------------------------------------
Would that work for you? Note that it will move the srom class devices
one level deeper in /sys/devices/... hierarchy.
Paweł
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