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    SubjectRe: [PATCH v5 2/5] can: kvaser_usb: Consolidate and unify state change handling
    Hi!

    On Wed, Jan 21, 2015 at 04:20:25PM +0000, Andri Yngvason wrote:
    > Quoting Ahmed S. Darwish (2015-01-20 21:45:37)
    > > From: Ahmed S. Darwish <ahmed.darwish@valeo.com>
    > >
    > > Replace most of the can interface's state and error counters
    > > handling with the new can-dev can_change_state() mechanism.
    > >
    > > Suggested-by: Andri Yngvason <andri.yngvason@marel.com>
    > > Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
    > > ---
    > > drivers/net/can/usb/kvaser_usb.c | 114 +++++++++++++++++++--------------------
    > > 1 file changed, 55 insertions(+), 59 deletions(-)
    > >
    > > diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c
    > > index 971c5f9..0386d3f 100644
    > > --- a/drivers/net/can/usb/kvaser_usb.c
    > > +++ b/drivers/net/can/usb/kvaser_usb.c
    > > @@ -620,40 +620,43 @@ static void kvaser_usb_unlink_tx_urbs(struct kvaser_usb_net_priv *priv)
    > > }
    > >
    > > static void kvaser_usb_rx_error_update_can_state(struct kvaser_usb_net_priv *priv,
    > > - const struct kvaser_usb_error_summary *es)
    > > + const struct kvaser_usb_error_summary *es,
    > > + struct can_frame *cf)
    > > {
    > > struct net_device_stats *stats;
    > > - enum can_state new_state;
    > > -
    > > - stats = &priv->netdev->stats;
    > > - new_state = priv->can.state;
    > > + enum can_state cur_state, new_state, tx_state, rx_state;
    > >
    > > netdev_dbg(priv->netdev, "Error status: 0x%02x\n", es->status);
    > >
    > > - if (es->status & M16C_STATE_BUS_OFF) {
    > > - priv->can.can_stats.bus_off++;
    > > + stats = &priv->netdev->stats;
    > > + new_state = cur_state = priv->can.state;
    > > +
    > > + if (es->status & M16C_STATE_BUS_OFF)
    > > new_state = CAN_STATE_BUS_OFF;
    > > - } else if (es->status & M16C_STATE_BUS_PASSIVE) {
    > > - if (priv->can.state != CAN_STATE_ERROR_PASSIVE)
    > > - priv->can.can_stats.error_passive++;
    > > + else if (es->status & M16C_STATE_BUS_PASSIVE)
    > > new_state = CAN_STATE_ERROR_PASSIVE;
    > > - }
    > >
    > > if (es->status == M16C_STATE_BUS_ERROR) {
    > > - if ((priv->can.state < CAN_STATE_ERROR_WARNING) &&
    > > - ((es->txerr >= 96) || (es->rxerr >= 96))) {
    > > - priv->can.can_stats.error_warning++;
    > > + if ((cur_state < CAN_STATE_ERROR_WARNING) &&
    > > + ((es->txerr >= 96) || (es->rxerr >= 96)))
    > > new_state = CAN_STATE_ERROR_WARNING;
    > > - } else if (priv->can.state > CAN_STATE_ERROR_ACTIVE) {
    > > + else if (cur_state > CAN_STATE_ERROR_ACTIVE)
    > > new_state = CAN_STATE_ERROR_ACTIVE;
    > > - }
    > > }
    > >
    > > if (!es->status)
    > > new_state = CAN_STATE_ERROR_ACTIVE;
    > >
    > > + if (new_state != cur_state) {
    > > + tx_state = (es->txerr >= es->rxerr) ? new_state : 0;
    > > + rx_state = (es->txerr <= es->rxerr) ? new_state : 0;
    > > +
    > > + can_change_state(priv->netdev, cf, tx_state, rx_state);
    >
    > This (below) is redundant. It doesn't harm but at this point can_change_state
    > has set priv->can.state to new_state.
    >
    > > + new_state = priv->can.state;
    > > + }
    > > +

    Correct; I will remove it.

    > > if (priv->can.restart_ms &&
    > > - (priv->can.state >= CAN_STATE_BUS_OFF) &&
    > > + (cur_state >= CAN_STATE_BUS_OFF) &&
    > > (new_state < CAN_STATE_BUS_OFF)) {
    > > priv->can.can_stats.restarts++;
    > > }
    > > @@ -665,18 +668,17 @@ static void kvaser_usb_rx_error_update_can_state(struct kvaser_usb_net_priv *pri
    > >
    > > priv->bec.txerr = es->txerr;
    > > priv->bec.rxerr = es->rxerr;
    > > - priv->can.state = new_state;
    > > }
    > >
    > > static void kvaser_usb_rx_error(const struct kvaser_usb *dev,
    > > const struct kvaser_msg *msg)
    > > {
    > > - struct can_frame *cf;
    > > + struct can_frame *cf, tmp_cf = { .can_id = CAN_ERR_FLAG, .can_dlc = CAN_ERR_DLC };
    > > struct sk_buff *skb;
    > > struct net_device_stats *stats;
    > > struct kvaser_usb_net_priv *priv;
    > > struct kvaser_usb_error_summary es = { };
    > > - enum can_state old_state;
    > > + enum can_state old_state, new_state;
    > >
    > > switch (msg->id) {
    > > case CMD_CAN_ERROR_EVENT:
    > > @@ -721,60 +723,54 @@ static void kvaser_usb_rx_error(const struct kvaser_usb *dev,
    > > }
    > >
    > > /* Update all of the can interface's state and error counters before
    > > - * trying any skb allocation that can actually fail with -ENOMEM.
    > > + * trying any memory allocation that can actually fail with -ENOMEM.
    > > + *
    > > + * We send a temporary stack-allocated error can frame to
    > > + * can_change_state() for the very same reason.
    > > + *
    > > + * TODO: Split can_change_state() responsibility between updating the
    > > + * can interface's state and counters, and the setting up of can error
    > > + * frame ID and data to userspace. Remove stack allocation afterwards.
    > > */
    > > old_state = priv->can.state;
    > > - kvaser_usb_rx_error_update_can_state(priv, &es);
    > > + kvaser_usb_rx_error_update_can_state(priv, &es, &tmp_cf);
    > > + new_state = priv->can.state;
    > >
    > > skb = alloc_can_err_skb(priv->netdev, &cf);
    > > if (!skb) {
    > > stats->rx_dropped++;
    > > return;
    > > }
    > > + memcpy(cf, &tmp_cf, sizeof(*cf));
    > >
    > > - if (es.status & M16C_STATE_BUS_OFF) {
    > > - cf->can_id |= CAN_ERR_BUSOFF;
    > > -
    > > - if (!priv->can.restart_ms)
    > > - kvaser_usb_simple_msg_async(priv, CMD_STOP_CHIP);
    > > - netif_carrier_off(priv->netdev);
    > > - } else if (es.status & M16C_STATE_BUS_PASSIVE) {
    > > - if (old_state != CAN_STATE_ERROR_PASSIVE) {
    > > - cf->can_id |= CAN_ERR_CRTL;
    > > -
    > > - if (es.txerr || es.rxerr)
    > > - cf->data[1] = (es.txerr > es.rxerr)
    > > - ? CAN_ERR_CRTL_TX_PASSIVE
    > > - : CAN_ERR_CRTL_RX_PASSIVE;
    > > - else
    > > - cf->data[1] = CAN_ERR_CRTL_TX_PASSIVE |
    > > - CAN_ERR_CRTL_RX_PASSIVE;
    > > + if (new_state != old_state) {
    > > + if (es.status & M16C_STATE_BUS_OFF) {
    > > + if (!priv->can.restart_ms)
    > > + kvaser_usb_simple_msg_async(priv, CMD_STOP_CHIP);
    > > + netif_carrier_off(priv->netdev);
    > > + }
    > > +
    >
    > This block [below] is wrong. The usage of PROT_ACTIVE is based on a misunderstanding.
    > It's used in some drivers to signify back-to-error-active but its original
    > meaning is something completely different, AFAIK.
    > This is handled in can_change_state() using a new CTRL message; namely:
    > CAN_ERR_CTRL_ACTIVE. The newest version of can-utils is up to date with this.
    >
    > > + if (es.status == M16C_STATE_BUS_ERROR) {
    > > + if ((old_state >= CAN_STATE_ERROR_WARNING) ||
    > > + (es.txerr < 96 && es.rxerr < 96)) {
    > > + if (old_state > CAN_STATE_ERROR_ACTIVE) {
    > > + cf->can_id |= CAN_ERR_PROT;
    > > + cf->data[2] = CAN_ERR_PROT_ACTIVE;
    > > + }
    > > + }
    > > }

    So I would just make the new_state equals CAN_STATE_ERROR_ACTIVE,
    and then can_change_state() will do the right thing? Excellent!!
    This means the entire block above can be removed ;-)

    [ On another note, the block's if conditions above are faulty and
    fixed in patch #3. This patch (#2) used can_change_state()
    without changing any of that faulty logic to ease any future
    bisection. ]

    > > - }
    > >
    > > - if (es.status == M16C_STATE_BUS_ERROR) {
    > > - if ((old_state < CAN_STATE_ERROR_WARNING) &&
    > > - ((es.txerr >= 96) || (es.rxerr >= 96))) {
    > > - cf->can_id |= CAN_ERR_CRTL;
    > > - cf->data[1] = (es.txerr > es.rxerr)
    > > - ? CAN_ERR_CRTL_TX_WARNING
    > > - : CAN_ERR_CRTL_RX_WARNING;
    > > - } else if (old_state > CAN_STATE_ERROR_ACTIVE) {
    >
    > This is also redundant, and wrong:
    >
    > > + if (!es.status) {
    > > cf->can_id |= CAN_ERR_PROT;
    > > cf->data[2] = CAN_ERR_PROT_ACTIVE;
    > > }
    > > - }

    As in the above; extra code to be removed, yay! ;-)

    > >
    > > - if (!es.status) {
    > > - cf->can_id |= CAN_ERR_PROT;
    > > - cf->data[2] = CAN_ERR_PROT_ACTIVE;
    > > - }
    > > -
    > > - if (priv->can.restart_ms &&
    > > - (old_state >= CAN_STATE_BUS_OFF) &&
    > > - (priv->can.state < CAN_STATE_BUS_OFF)) {
    > > - cf->can_id |= CAN_ERR_RESTARTED;
    > > - netif_carrier_on(priv->netdev);
    > > + if (priv->can.restart_ms &&
    > > + (old_state >= CAN_STATE_BUS_OFF) &&
    > > + (new_state < CAN_STATE_BUS_OFF)) {
    > > + cf->can_id |= CAN_ERR_RESTARTED;
    > > + netif_carrier_on(priv->netdev);
    > > + }
    > > }
    > >
    > > if (es.error_factor) {
    > > --
    > > 1.9.1
    >
    > Looking over the patch again, I've noticed that there
    > are a few things that are not quite right.
    >

    The state-handlig code has become much simpler since your
    reveiw and Kleine-Budde's one. Thanks a lot for all the effort.

    Regards,
    Darwish


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