On Wed, 21 May 2008 17:04:56 -0700 David Brownell <[EMAIL PROTECTED]> wrote:
> From: Grant Likely <[EMAIL PROTECTED]>
>
> Currently, 'modalias' in the spi_device structure is a 'const char *'.
> The spi_new_device() function fills in the modalias value from a passed
> in spi_board_info data block. Since it is a pointer copy, the new
> spi_device remains dependent on the spi_board_info structure after the
> new spi_device is registered (no other fields in spi_device directly
> depend on the spi_board_info structure; all of the other data is copied).
>
> This causes a problem when dynamically propulating the list of attached
> SPI devices. For example, in arch/powerpc, the list of SPI devices can
> be populated from data in the device tree. With the current code, the
> device tree adapter must kmalloc() a new spi_board_info structure for
> each new SPI device it finds in the device tree, and there is no simple
> mechanism in place for keeping track of these allocations.
>
> This patch changes modalias from a 'const char *' to a fixed char array.
> By copying the modalias string instead of referencing it, the dependency
> on the spi_board_info structure is eliminated and an outside caller does
> not need to maintain a separate spi_board_info allocation for each device.
>
> If searched through the code to the best of my ability for any references
> to modalias which may be affected by this change and haven't found anything.
> It has been tested with the lite5200b platform in arch/powerpc.
>
Not for 2.6.26, I assume?
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -229,7 +229,7 @@ struct spi_device *spi_new_device(struct spi_master
> *master,
> proxy->max_speed_hz = chip->max_speed_hz;
> proxy->mode = chip->mode;
> proxy->irq = chip->irq;
> - proxy->modalias = chip->modalias;
> + strncpy(proxy->modalias, chip->modalias, KOBJ_NAME_LEN);
>
> snprintf(proxy->dev.bus_id, sizeof proxy->dev.bus_id,
> "%s.%u", master->dev.bus_id,
> --- a/include/linux/spi/spi.h
> +++ b/include/linux/spi/spi.h
> @@ -82,7 +82,7 @@ struct spi_device {
> int irq;
> void *controller_state;
> void *controller_data;
> - const char *modalias;
> + char modalias[KOBJ_NAME_LEN];
>
> /*
> * likely need more hooks for more protocol options affecting how
a) strncpy() doesn't null-terminate the dest if it overran. strlcpy() does.
b) Given the uncertainly over the state of existing code, perhaps we
should have an explicit check for overflows here, with a WARN_ON()?
c) I think it's better to use sizeof() in the strlcpy() rather than
duplicating the array size - it's a little more robust in the face
of future changes and it is more obviously-correct (don't need to go
elsewhere to check the size of the destination).
d) KOBJ_NAME_LEN no longer exists in linux-next. I'm not sure where
it went - Greg and Kay have been up to their usual tricks.
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