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can: gw: support modification of Classical CAN DLCs
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Add support for data length code modifications for Classical CAN.

The netlink configuration interface always allowed to pass any value
that fits into a byte, therefore only the modification process had to be
extended to handle the raw DLC represenation of Classical CAN frames.

When a DLC value from 0 .. F is provided for Classical CAN frame
modifications the 'len' value is modified as-is with the exception that
potentially existing 9 .. F DLC values in the len8_dlc element are moved
to the 'len' element for the modification operation by mod_retrieve_ccdlc().

After the modification the Classical CAN frame DLC information is brought
back into the correct format by mod_store_ccdlc() which is filling 'len'
and 'len8_dlc' accordingly.

Signed-off-by: Oliver Hartkopp <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Marc Kleine-Budde <[email protected]>
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@hartkopp @marckleinebudde
hartkopp authored and marckleinebudde committed Nov 20, 2020
1 parent 396b3ce commit 94c2309
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Showing 2 changed files with 72 additions and 10 deletions.
4 changes: 2 additions & 2 deletions include/uapi/linux/can/gw.h
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Original file line number Diff line number Diff line change
Expand Up @@ -98,8 +98,8 @@ enum {

/* CAN frame elements that are affected by curr. 3 CAN frame modifications */
#define CGW_MOD_ID 0x01
#define CGW_MOD_DLC 0x02 /* contains the data length in bytes */
#define CGW_MOD_LEN CGW_MOD_DLC /* CAN FD length representation */
#define CGW_MOD_DLC 0x02 /* Classical CAN data length code */
#define CGW_MOD_LEN CGW_MOD_DLC /* CAN FD (plain) data length */
#define CGW_MOD_DATA 0x04
#define CGW_MOD_FLAGS 0x08 /* CAN FD flags */

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78 changes: 70 additions & 8 deletions net/can/gw.c
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Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,68 @@ static void mod_set_fddata(struct canfd_frame *cf, struct cf_mod *mod)
memcpy(cf->data, mod->modframe.set.data, CANFD_MAX_DLEN);
}

/* retrieve valid CC DLC value and store it into 'len' */
static void mod_retrieve_ccdlc(struct canfd_frame *cf)
{
struct can_frame *ccf = (struct can_frame *)cf;

/* len8_dlc is only valid if len == CAN_MAX_DLEN */
if (ccf->len != CAN_MAX_DLEN)
return;

/* do we have a valid len8_dlc value from 9 .. 15 ? */
if (ccf->len8_dlc > CAN_MAX_DLEN && ccf->len8_dlc <= CAN_MAX_RAW_DLC)
ccf->len = ccf->len8_dlc;
}

/* convert valid CC DLC value in 'len' into struct can_frame elements */
static void mod_store_ccdlc(struct canfd_frame *cf)
{
struct can_frame *ccf = (struct can_frame *)cf;

/* clear potential leftovers */
ccf->len8_dlc = 0;

/* plain data length 0 .. 8 - that was easy */
if (ccf->len <= CAN_MAX_DLEN)
return;

/* potentially broken values are catched in can_can_gw_rcv() */
if (ccf->len > CAN_MAX_RAW_DLC)
return;

/* we have a valid dlc value from 9 .. 15 in ccf->len */
ccf->len8_dlc = ccf->len;
ccf->len = CAN_MAX_DLEN;
}

static void mod_and_ccdlc(struct canfd_frame *cf, struct cf_mod *mod)
{
mod_retrieve_ccdlc(cf);
mod_and_len(cf, mod);
mod_store_ccdlc(cf);
}

static void mod_or_ccdlc(struct canfd_frame *cf, struct cf_mod *mod)
{
mod_retrieve_ccdlc(cf);
mod_or_len(cf, mod);
mod_store_ccdlc(cf);
}

static void mod_xor_ccdlc(struct canfd_frame *cf, struct cf_mod *mod)
{
mod_retrieve_ccdlc(cf);
mod_xor_len(cf, mod);
mod_store_ccdlc(cf);
}

static void mod_set_ccdlc(struct canfd_frame *cf, struct cf_mod *mod)
{
mod_set_len(cf, mod);
mod_store_ccdlc(cf);
}

static void canframecpy(struct canfd_frame *dst, struct can_frame *src)
{
/* Copy the struct members separately to ensure that no uninitialized
Expand Down Expand Up @@ -842,8 +904,8 @@ static int cgw_parse_attr(struct nlmsghdr *nlh, struct cf_mod *mod,
if (mb.modtype & CGW_MOD_ID)
mod->modfunc[modidx++] = mod_and_id;

if (mb.modtype & CGW_MOD_LEN)
mod->modfunc[modidx++] = mod_and_len;
if (mb.modtype & CGW_MOD_DLC)
mod->modfunc[modidx++] = mod_and_ccdlc;

if (mb.modtype & CGW_MOD_DATA)
mod->modfunc[modidx++] = mod_and_data;
Expand All @@ -858,8 +920,8 @@ static int cgw_parse_attr(struct nlmsghdr *nlh, struct cf_mod *mod,
if (mb.modtype & CGW_MOD_ID)
mod->modfunc[modidx++] = mod_or_id;

if (mb.modtype & CGW_MOD_LEN)
mod->modfunc[modidx++] = mod_or_len;
if (mb.modtype & CGW_MOD_DLC)
mod->modfunc[modidx++] = mod_or_ccdlc;

if (mb.modtype & CGW_MOD_DATA)
mod->modfunc[modidx++] = mod_or_data;
Expand All @@ -874,8 +936,8 @@ static int cgw_parse_attr(struct nlmsghdr *nlh, struct cf_mod *mod,
if (mb.modtype & CGW_MOD_ID)
mod->modfunc[modidx++] = mod_xor_id;

if (mb.modtype & CGW_MOD_LEN)
mod->modfunc[modidx++] = mod_xor_len;
if (mb.modtype & CGW_MOD_DLC)
mod->modfunc[modidx++] = mod_xor_ccdlc;

if (mb.modtype & CGW_MOD_DATA)
mod->modfunc[modidx++] = mod_xor_data;
Expand All @@ -890,8 +952,8 @@ static int cgw_parse_attr(struct nlmsghdr *nlh, struct cf_mod *mod,
if (mb.modtype & CGW_MOD_ID)
mod->modfunc[modidx++] = mod_set_id;

if (mb.modtype & CGW_MOD_LEN)
mod->modfunc[modidx++] = mod_set_len;
if (mb.modtype & CGW_MOD_DLC)
mod->modfunc[modidx++] = mod_set_ccdlc;

if (mb.modtype & CGW_MOD_DATA)
mod->modfunc[modidx++] = mod_set_data;
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