Re: [PATCH RFC FINAL v5] media: OF: add "sync-on-green-active" property
Hi Hans, Thanks for the review. On Fri, Jul 26, 2013 at 3:27 PM, Hans Verkuil wrote: > Hi Prabhakar, > > On 07/17/2013 05:47 PM, Prabhakar Lad wrote: >> From: "Lad, Prabhakar" >> >> This patch adds 'sync-on-green-active' property as part >> of endpoint property. >> >> Signed-off-by: Lad, Prabhakar >> --- >> Changes for v5: >> 1: Changed description for sync-on-green-active property in >> documentation file as suggested by Sylwester. >> >> Changes for v4: >> 1: Fixed review comments pointed by Sylwester. >> >> Changes for v3: >> 1: Fixed review comments pointed by Laurent and Sylwester. >> >> RFC v2 https://patchwork.kernel.org/patch/2578091/ >> >> RFC V1 https://patchwork.kernel.org/patch/2572341/ >> >> .../devicetree/bindings/media/video-interfaces.txt |2 ++ >> drivers/media/v4l2-core/v4l2-of.c |4 >> include/media/v4l2-mediabus.h |2 ++ >> 3 files changed, 8 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt >> b/Documentation/devicetree/bindings/media/video-interfaces.txt >> index e022d2d..ce719f8 100644 >> --- a/Documentation/devicetree/bindings/media/video-interfaces.txt >> +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt >> @@ -88,6 +88,8 @@ Optional endpoint properties >> - field-even-active: field signal level during the even field data >> transmission. >> - pclk-sample: sample data on rising (1) or falling (0) edge of the pixel >> clock >>signal. >> +- sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for >> + LOW/HIGH respectively. >> - data-lanes: an array of physical data lane indexes. Position of an entry >>determines the logical lane number, while the value of an entry indicates >>physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have >> diff --git a/drivers/media/v4l2-core/v4l2-of.c >> b/drivers/media/v4l2-core/v4l2-of.c >> index aa59639..5c4c9f0 100644 >> --- a/drivers/media/v4l2-core/v4l2-of.c >> +++ b/drivers/media/v4l2-core/v4l2-of.c >> @@ -100,6 +100,10 @@ static void v4l2_of_parse_parallel_bus(const struct >> device_node *node, >> if (!of_property_read_u32(node, "data-shift", )) >> bus->data_shift = v; >> >> + if (!of_property_read_u32(node, "sync-on-green-active", )) >> + flags |= v ? V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH : >> + V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW; >> + >> bus->flags = flags; >> >> } >> diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h >> index 83ae07e..d47eb81 100644 >> --- a/include/media/v4l2-mediabus.h >> +++ b/include/media/v4l2-mediabus.h >> @@ -40,6 +40,8 @@ >> #define V4L2_MBUS_FIELD_EVEN_HIGH(1 << 10) >> /* FIELD = 1/0 - Field1 (odd)/Field2 (even) */ >> #define V4L2_MBUS_FIELD_EVEN_LOW (1 << 11) >> +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH (1 << 12) >> +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW (1 << 13) > > Can you add a short comment for these new flags? Similar to what you added in > video-interfaces.txt? > OK will fix it and repost. Regards, --Prabhakar Lad -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH RFC FINAL v5] media: OF: add "sync-on-green-active" property
Hi Prabhakar, On 07/17/2013 05:47 PM, Prabhakar Lad wrote: > From: "Lad, Prabhakar" > > This patch adds 'sync-on-green-active' property as part > of endpoint property. > > Signed-off-by: Lad, Prabhakar > --- > Changes for v5: > 1: Changed description for sync-on-green-active property in > documentation file as suggested by Sylwester. > > Changes for v4: > 1: Fixed review comments pointed by Sylwester. > > Changes for v3: > 1: Fixed review comments pointed by Laurent and Sylwester. > > RFC v2 https://patchwork.kernel.org/patch/2578091/ > > RFC V1 https://patchwork.kernel.org/patch/2572341/ > > .../devicetree/bindings/media/video-interfaces.txt |2 ++ > drivers/media/v4l2-core/v4l2-of.c |4 > include/media/v4l2-mediabus.h |2 ++ > 3 files changed, 8 insertions(+) > > diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt > b/Documentation/devicetree/bindings/media/video-interfaces.txt > index e022d2d..ce719f8 100644 > --- a/Documentation/devicetree/bindings/media/video-interfaces.txt > +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt > @@ -88,6 +88,8 @@ Optional endpoint properties > - field-even-active: field signal level during the even field data > transmission. > - pclk-sample: sample data on rising (1) or falling (0) edge of the pixel > clock >signal. > +- sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for > + LOW/HIGH respectively. > - data-lanes: an array of physical data lane indexes. Position of an entry >determines the logical lane number, while the value of an entry indicates >physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have > diff --git a/drivers/media/v4l2-core/v4l2-of.c > b/drivers/media/v4l2-core/v4l2-of.c > index aa59639..5c4c9f0 100644 > --- a/drivers/media/v4l2-core/v4l2-of.c > +++ b/drivers/media/v4l2-core/v4l2-of.c > @@ -100,6 +100,10 @@ static void v4l2_of_parse_parallel_bus(const struct > device_node *node, > if (!of_property_read_u32(node, "data-shift", )) > bus->data_shift = v; > > + if (!of_property_read_u32(node, "sync-on-green-active", )) > + flags |= v ? V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH : > + V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW; > + > bus->flags = flags; > > } > diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h > index 83ae07e..d47eb81 100644 > --- a/include/media/v4l2-mediabus.h > +++ b/include/media/v4l2-mediabus.h > @@ -40,6 +40,8 @@ > #define V4L2_MBUS_FIELD_EVEN_HIGH(1 << 10) > /* FIELD = 1/0 - Field1 (odd)/Field2 (even) */ > #define V4L2_MBUS_FIELD_EVEN_LOW (1 << 11) > +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH (1 << 12) > +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW (1 << 13) Can you add a short comment for these new flags? Similar to what you added in video-interfaces.txt? Thanks! Hans > > /* Serial flags */ > /* How many lanes the client can use */ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH RFC FINAL v5] media: OF: add sync-on-green-active property
Hi Prabhakar, On 07/17/2013 05:47 PM, Prabhakar Lad wrote: From: Lad, Prabhakar prabhakar.cse...@gmail.com This patch adds 'sync-on-green-active' property as part of endpoint property. Signed-off-by: Lad, Prabhakar prabhakar.cse...@gmail.com --- Changes for v5: 1: Changed description for sync-on-green-active property in documentation file as suggested by Sylwester. Changes for v4: 1: Fixed review comments pointed by Sylwester. Changes for v3: 1: Fixed review comments pointed by Laurent and Sylwester. RFC v2 https://patchwork.kernel.org/patch/2578091/ RFC V1 https://patchwork.kernel.org/patch/2572341/ .../devicetree/bindings/media/video-interfaces.txt |2 ++ drivers/media/v4l2-core/v4l2-of.c |4 include/media/v4l2-mediabus.h |2 ++ 3 files changed, 8 insertions(+) diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt b/Documentation/devicetree/bindings/media/video-interfaces.txt index e022d2d..ce719f8 100644 --- a/Documentation/devicetree/bindings/media/video-interfaces.txt +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt @@ -88,6 +88,8 @@ Optional endpoint properties - field-even-active: field signal level during the even field data transmission. - pclk-sample: sample data on rising (1) or falling (0) edge of the pixel clock signal. +- sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for + LOW/HIGH respectively. - data-lanes: an array of physical data lane indexes. Position of an entry determines the logical lane number, while the value of an entry indicates physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have diff --git a/drivers/media/v4l2-core/v4l2-of.c b/drivers/media/v4l2-core/v4l2-of.c index aa59639..5c4c9f0 100644 --- a/drivers/media/v4l2-core/v4l2-of.c +++ b/drivers/media/v4l2-core/v4l2-of.c @@ -100,6 +100,10 @@ static void v4l2_of_parse_parallel_bus(const struct device_node *node, if (!of_property_read_u32(node, data-shift, v)) bus-data_shift = v; + if (!of_property_read_u32(node, sync-on-green-active, v)) + flags |= v ? V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH : + V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW; + bus-flags = flags; } diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h index 83ae07e..d47eb81 100644 --- a/include/media/v4l2-mediabus.h +++ b/include/media/v4l2-mediabus.h @@ -40,6 +40,8 @@ #define V4L2_MBUS_FIELD_EVEN_HIGH(1 10) /* FIELD = 1/0 - Field1 (odd)/Field2 (even) */ #define V4L2_MBUS_FIELD_EVEN_LOW (1 11) +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH (1 12) +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW (1 13) Can you add a short comment for these new flags? Similar to what you added in video-interfaces.txt? Thanks! Hans /* Serial flags */ /* How many lanes the client can use */ -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH RFC FINAL v5] media: OF: add sync-on-green-active property
Hi Hans, Thanks for the review. On Fri, Jul 26, 2013 at 3:27 PM, Hans Verkuil hverk...@xs4all.nl wrote: Hi Prabhakar, On 07/17/2013 05:47 PM, Prabhakar Lad wrote: From: Lad, Prabhakar prabhakar.cse...@gmail.com This patch adds 'sync-on-green-active' property as part of endpoint property. Signed-off-by: Lad, Prabhakar prabhakar.cse...@gmail.com --- Changes for v5: 1: Changed description for sync-on-green-active property in documentation file as suggested by Sylwester. Changes for v4: 1: Fixed review comments pointed by Sylwester. Changes for v3: 1: Fixed review comments pointed by Laurent and Sylwester. RFC v2 https://patchwork.kernel.org/patch/2578091/ RFC V1 https://patchwork.kernel.org/patch/2572341/ .../devicetree/bindings/media/video-interfaces.txt |2 ++ drivers/media/v4l2-core/v4l2-of.c |4 include/media/v4l2-mediabus.h |2 ++ 3 files changed, 8 insertions(+) diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt b/Documentation/devicetree/bindings/media/video-interfaces.txt index e022d2d..ce719f8 100644 --- a/Documentation/devicetree/bindings/media/video-interfaces.txt +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt @@ -88,6 +88,8 @@ Optional endpoint properties - field-even-active: field signal level during the even field data transmission. - pclk-sample: sample data on rising (1) or falling (0) edge of the pixel clock signal. +- sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for + LOW/HIGH respectively. - data-lanes: an array of physical data lane indexes. Position of an entry determines the logical lane number, while the value of an entry indicates physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have diff --git a/drivers/media/v4l2-core/v4l2-of.c b/drivers/media/v4l2-core/v4l2-of.c index aa59639..5c4c9f0 100644 --- a/drivers/media/v4l2-core/v4l2-of.c +++ b/drivers/media/v4l2-core/v4l2-of.c @@ -100,6 +100,10 @@ static void v4l2_of_parse_parallel_bus(const struct device_node *node, if (!of_property_read_u32(node, data-shift, v)) bus-data_shift = v; + if (!of_property_read_u32(node, sync-on-green-active, v)) + flags |= v ? V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH : + V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW; + bus-flags = flags; } diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h index 83ae07e..d47eb81 100644 --- a/include/media/v4l2-mediabus.h +++ b/include/media/v4l2-mediabus.h @@ -40,6 +40,8 @@ #define V4L2_MBUS_FIELD_EVEN_HIGH(1 10) /* FIELD = 1/0 - Field1 (odd)/Field2 (even) */ #define V4L2_MBUS_FIELD_EVEN_LOW (1 11) +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH (1 12) +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW (1 13) Can you add a short comment for these new flags? Similar to what you added in video-interfaces.txt? OK will fix it and repost. Regards, --Prabhakar Lad -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH RFC FINAL v5] media: OF: add "sync-on-green-active" property
Hi Sylwester, On Wed, Jul 17, 2013 at 9:50 PM, Sylwester Nawrocki wrote: > On 07/17/2013 05:47 PM, Prabhakar Lad wrote: >> From: "Lad, Prabhakar" >> >> This patch adds 'sync-on-green-active' property as part >> of endpoint property. >> >> Signed-off-by: Lad, Prabhakar > > Thanks Prabhakar, it looks good to me. > Just a side note, the 'From' tag above isn't needed. It wasn't > added automatically, was it ? Yes this was added automatically. > Unless there are comments from others I think this patch should > be merged together with the users of this new property. > > Acked-by: Sylwester Nawrocki > Thanks for the Ack. -- Regards, Prabhakar Lad -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH RFC FINAL v5] media: OF: add "sync-on-green-active" property
On 07/17/2013 05:47 PM, Prabhakar Lad wrote: > From: "Lad, Prabhakar" > > This patch adds 'sync-on-green-active' property as part > of endpoint property. > > Signed-off-by: Lad, Prabhakar Thanks Prabhakar, it looks good to me. Just a side note, the 'From' tag above isn't needed. It wasn't added automatically, was it ? Unless there are comments from others I think this patch should be merged together with the users of this new property. Acked-by: Sylwester Nawrocki Regards, Sylwester > --- > Changes for v5: > 1: Changed description for sync-on-green-active property in > documentation file as suggested by Sylwester. > > Changes for v4: > 1: Fixed review comments pointed by Sylwester. > > Changes for v3: > 1: Fixed review comments pointed by Laurent and Sylwester. > > RFC v2 https://patchwork.kernel.org/patch/2578091/ > > RFC V1 https://patchwork.kernel.org/patch/2572341/ > > .../devicetree/bindings/media/video-interfaces.txt |2 ++ > drivers/media/v4l2-core/v4l2-of.c |4 > include/media/v4l2-mediabus.h |2 ++ > 3 files changed, 8 insertions(+) > > diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt > b/Documentation/devicetree/bindings/media/video-interfaces.txt > index e022d2d..ce719f8 100644 > --- a/Documentation/devicetree/bindings/media/video-interfaces.txt > +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt > @@ -88,6 +88,8 @@ Optional endpoint properties > - field-even-active: field signal level during the even field data > transmission. > - pclk-sample: sample data on rising (1) or falling (0) edge of the pixel > clock >signal. > +- sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for > + LOW/HIGH respectively. > - data-lanes: an array of physical data lane indexes. Position of an entry >determines the logical lane number, while the value of an entry indicates >physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have > diff --git a/drivers/media/v4l2-core/v4l2-of.c > b/drivers/media/v4l2-core/v4l2-of.c > index aa59639..5c4c9f0 100644 > --- a/drivers/media/v4l2-core/v4l2-of.c > +++ b/drivers/media/v4l2-core/v4l2-of.c > @@ -100,6 +100,10 @@ static void v4l2_of_parse_parallel_bus(const struct > device_node *node, > if (!of_property_read_u32(node, "data-shift", )) > bus->data_shift = v; > > + if (!of_property_read_u32(node, "sync-on-green-active", )) > + flags |= v ? V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH : > + V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW; > + > bus->flags = flags; > > } > diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h > index 83ae07e..d47eb81 100644 > --- a/include/media/v4l2-mediabus.h > +++ b/include/media/v4l2-mediabus.h > @@ -40,6 +40,8 @@ > #define V4L2_MBUS_FIELD_EVEN_HIGH(1 << 10) > /* FIELD = 1/0 - Field1 (odd)/Field2 (even) */ > #define V4L2_MBUS_FIELD_EVEN_LOW (1 << 11) > +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH (1 << 12) > +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW (1 << 13) > > /* Serial flags */ > /* How many lanes the client can use */ > -- Sylwester Nawrocki Samsung R Institute Poland -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH RFC FINAL v5] media: OF: add sync-on-green-active property
On 07/17/2013 05:47 PM, Prabhakar Lad wrote: From: Lad, Prabhakar prabhakar.cse...@gmail.com This patch adds 'sync-on-green-active' property as part of endpoint property. Signed-off-by: Lad, Prabhakar prabhakar.cse...@gmail.com Thanks Prabhakar, it looks good to me. Just a side note, the 'From' tag above isn't needed. It wasn't added automatically, was it ? Unless there are comments from others I think this patch should be merged together with the users of this new property. Acked-by: Sylwester Nawrocki s.nawro...@samsung.com Regards, Sylwester --- Changes for v5: 1: Changed description for sync-on-green-active property in documentation file as suggested by Sylwester. Changes for v4: 1: Fixed review comments pointed by Sylwester. Changes for v3: 1: Fixed review comments pointed by Laurent and Sylwester. RFC v2 https://patchwork.kernel.org/patch/2578091/ RFC V1 https://patchwork.kernel.org/patch/2572341/ .../devicetree/bindings/media/video-interfaces.txt |2 ++ drivers/media/v4l2-core/v4l2-of.c |4 include/media/v4l2-mediabus.h |2 ++ 3 files changed, 8 insertions(+) diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt b/Documentation/devicetree/bindings/media/video-interfaces.txt index e022d2d..ce719f8 100644 --- a/Documentation/devicetree/bindings/media/video-interfaces.txt +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt @@ -88,6 +88,8 @@ Optional endpoint properties - field-even-active: field signal level during the even field data transmission. - pclk-sample: sample data on rising (1) or falling (0) edge of the pixel clock signal. +- sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for + LOW/HIGH respectively. - data-lanes: an array of physical data lane indexes. Position of an entry determines the logical lane number, while the value of an entry indicates physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have diff --git a/drivers/media/v4l2-core/v4l2-of.c b/drivers/media/v4l2-core/v4l2-of.c index aa59639..5c4c9f0 100644 --- a/drivers/media/v4l2-core/v4l2-of.c +++ b/drivers/media/v4l2-core/v4l2-of.c @@ -100,6 +100,10 @@ static void v4l2_of_parse_parallel_bus(const struct device_node *node, if (!of_property_read_u32(node, data-shift, v)) bus-data_shift = v; + if (!of_property_read_u32(node, sync-on-green-active, v)) + flags |= v ? V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH : + V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW; + bus-flags = flags; } diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h index 83ae07e..d47eb81 100644 --- a/include/media/v4l2-mediabus.h +++ b/include/media/v4l2-mediabus.h @@ -40,6 +40,8 @@ #define V4L2_MBUS_FIELD_EVEN_HIGH(1 10) /* FIELD = 1/0 - Field1 (odd)/Field2 (even) */ #define V4L2_MBUS_FIELD_EVEN_LOW (1 11) +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_HIGH (1 12) +#define V4L2_MBUS_VIDEO_SOG_ACTIVE_LOW (1 13) /* Serial flags */ /* How many lanes the client can use */ -- Sylwester Nawrocki Samsung RD Institute Poland -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH RFC FINAL v5] media: OF: add sync-on-green-active property
Hi Sylwester, On Wed, Jul 17, 2013 at 9:50 PM, Sylwester Nawrocki s.nawro...@samsung.com wrote: On 07/17/2013 05:47 PM, Prabhakar Lad wrote: From: Lad, Prabhakar prabhakar.cse...@gmail.com This patch adds 'sync-on-green-active' property as part of endpoint property. Signed-off-by: Lad, Prabhakar prabhakar.cse...@gmail.com Thanks Prabhakar, it looks good to me. Just a side note, the 'From' tag above isn't needed. It wasn't added automatically, was it ? Yes this was added automatically. Unless there are comments from others I think this patch should be merged together with the users of this new property. Acked-by: Sylwester Nawrocki s.nawro...@samsung.com Thanks for the Ack. -- Regards, Prabhakar Lad -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
