RE: [PATCH 1/2] device: add dma_params->max_segment_count

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


On Thursday, July 19, 2012 6:24 PM Rob Clark wrote:

> From: Rob Clark <rob@xxxxxx>
> For devices which have constraints about maximum number of segments
> in an sglist.  For example, a device which could only deal with
> contiguous buffers would set max_segment_count to 1.
> The initial motivation is for devices sharing buffers via dma-buf,
> to allow the buffer exporter to know the constraints of other
> devices which have attached to the buffer.  The dma_mask and fields
> in 'struct device_dma_parameters' tell the exporter everything else
> that is needed, except whether the importer has constraints about
> maximum number of segments.
> Signed-off-by: Rob Clark <rob@xxxxxx>

Yea, it is a really good idea to add this to struct device_dma_parameters.
We only need to initialize it to '1' in platform startup code for all 
devices relevant to buffer sharing.

Acked-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

> ---
>  include/linux/device.h      |    1 +
>  include/linux/dma-mapping.h |   16 ++++++++++++++++
>  2 files changed, 17 insertions(+)
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 161d962..3813735 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -568,6 +568,7 @@ struct device_dma_parameters {
>  	 * sg limitations.
>  	 */
>  	unsigned int max_segment_size;
> +	unsigned int max_segment_count;    /* zero for unlimited */
>  	unsigned long segment_boundary_mask;
>  };
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index dfc099e..f380f79 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -111,6 +111,22 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
>  		return -EIO;
>  }
> +static inline unsigned int dma_get_max_seg_count(struct device *dev)
> +{
> +	return dev->dma_parms ? dev->dma_parms->max_segment_count : 0;
> +}
> +
> +static inline int dma_set_max_seg_count(struct device *dev,
> +						unsigned int count)
> +{
> +	if (dev->dma_parms) {
> +		dev->dma_parms->max_segment_count = count;
> +		return 0;
> +	} else
> +		return -EIO;
> +}
> +
> +
>  static inline unsigned long dma_get_seg_boundary(struct device *dev)
>  {
>  	return dev->dma_parms ?
> --

Best regards
Marek Szyprowski
Samsung Poland R&D Center

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at

[Other Archives]     [Linux Kernel Newbies]     [Linux Driver Development]     [Linux Kbuild]     [Fedora Kernel]     [Linux Kernel Testers]     [Linux SH]     [Linux Omap]     [Linux Tape]     [Linux Input]     [Linux Kernel Janitors]     [Linux Kernel Packagers]     [Linux Doc]     [Linux Man Pages]     [Linux API]     [Linux Memory Management]     [Linux Modules]     [Linux Standards]     [Kernel Announce]     [Netdev]     [Git]     [Linux PCI]     Linux CAN Development     [Linux I2C]     [Linux RDMA]     [Linux NUMA]     [Netfilter]     [Netfilter Devel]     [SELinux]     [Bugtraq]     [FIO]     [Linux Perf Users]     [Linux Serial]     [Linux PPP]     [Linux ISDN]     [Linux Next]     [Kernel Stable Commits]     [Linux Tip Commits]     [Kernel MM Commits]     [Linux Security Module]     [AutoFS]     [Filesystem Development]     [Ext3 Filesystem]     [Linux bcache]     [Ext4 Filesystem]     [Linux BTRFS]     [Linux CEPH Filesystem]     [Linux XFS]     [XFS]     [Linux NFS]     [Linux CIFS]     [Ecryptfs]     [Linux NILFS]     [Linux Cachefs]     [Reiser FS]     [Initramfs]     [Linux FB Devel]     [Linux OpenGL]     [DRI Devel]     [Fastboot]     [Linux RT Users]     [Linux RT Stable]     [eCos]     [Corosync]     [Linux Clusters]     [LVS Devel]     [Hot Plug]     [Linux Virtualization]     [KVM]     [KVM PPC]     [KVM ia64]     [Linux Containers]     [Linux Hexagon]     [Linux Cgroups]     [Util Linux]     [Wireless]     [Linux Bluetooth]     [Bluez Devel]     [Ethernet Bridging]     [Embedded Linux]     [Barebox]     [Linux MMC]     [Linux IIO]     [Sparse]     [Smatch]     [Linux Arch]     [x86 Platform Driver]     [Linux ACPI]     [Linux IBM ACPI]     [LM Sensors]     [CPU Freq]     [Linux Power Management]     [Linmodems]     [Linux DCCP]     [Linux SCTP]     [ALSA Devel]     [Linux USB]     [Linux PA RISC]     [Linux Samsung SOC]     [MIPS Linux]     [IBM S/390 Linux]     [ARM Linux]     [ARM Kernel]     [ARM MSM]     [Tegra Devel]     [Sparc Linux]     [Linux Security]     [Linux Sound]     [Linux Media]     [Video 4 Linux]     [Linux IRDA Users]     [Linux for the blind]     [Linux RAID]     [Linux ATA RAID]     [Device Mapper]     [Linux SCSI]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Linux IDE]     [Linux SMP]     [Linux AXP]     [Linux Alpha]     [Linux M68K]     [Linux ia64]     [Linux 8086]     [Linux x86_64]     [Linux Config]     [Linux Apps]     [Linux MSDOS]     [Linux X.25]     [Linux Crypto]     [DM Crypt]     [Linux Trace Users]     [Linux Btrace]     [Linux Watchdog]     [Utrace Devel]     [Linux C Programming]     [Linux Assembly]     [Dash]     [DWARVES]     [Hail Devel]     [Linux Kernel Debugger]     [Linux gcc]     [Gcc Help]     [X.Org]     [Wine]

Add to Google Powered by Linux

[Older Kernel Discussion]     [Yosemite National Park Forum]     [Large Format Photos]     [Gimp]     [Yosemite Photos]     [Stuff]