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Date: Tue, 25 Oct 2022 14:04:44 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: "D. Starke" <daniel.starke@...mens.com>
Cc: linux-serial@...r.kernel.org, jirislaby@...nel.org,
ilpo.jarvinen@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] tty: n_gsm: add parameter negotiation support
On Mon, Oct 24, 2022 at 03:01:14PM +0200, D. Starke wrote:
> From: Daniel Starke <daniel.starke@...mens.com>
>
> n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
> See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
> The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
> the newer 27.010 here. Chapter 5.1.8.1.1 describes the parameter negotiation
> messages and parameters. Chapter 5.4.1 states that the default parameters
> are to be used if no negotiation is performed. Chapter 5.4.6.3.1 describes
> the encoding of the parameter negotiation message. The meaning of the
> parameters and allowed value ranges can be found in chapter 5.7.
>
> Add parameter negotiation support accordingly. DLCI specific parameter
> configuration by the user requires additional ioctls. This is subject to
> another patch.
>
> Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
> ---
> drivers/tty/n_gsm.c | 335 ++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 327 insertions(+), 8 deletions(-)
>
> v1 -> v2:
> Incorporated review comments.
> Simplification of command retry handling remains subject to future patches.
>
> Link: https://lore.kernel.org/all/8c2b9492-caf4-7a48-3a7b-da939a4ac8b6@linux.intel.com/
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index c217013b3e16..11d3730bf436 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -38,6 +38,7 @@
> #include <linux/sched/signal.h>
> #include <linux/interrupt.h>
> #include <linux/tty.h>
> +#include <linux/bitfield.h>
> #include <linux/ctype.h>
> #include <linux/mm.h>
> #include <linux/math.h>
> @@ -127,6 +128,7 @@ struct gsm_msg {
>
> enum gsm_dlci_state {
> DLCI_CLOSED,
> + DLCI_CONFIGURE, /* Sending PN (for adaption > 1) */
> DLCI_OPENING, /* Sending SABM not seen UA */
> DLCI_OPEN, /* SABM/UA complete */
> DLCI_CLOSING, /* Sending DISC not seen UA/DM */
> @@ -184,6 +186,30 @@ struct gsm_dlci {
> struct net_device *net; /* network interface, if created */
> };
>
> +/*
> + * Parameter bits used for parameter negotiation according to 3GPP 27.010
> + * chapter 5.4.6.3.1.
> + */
> +
> +struct gsm_dlci_param_bits {
> + u8 d_bits;
> + u8 i_cl_bits;
> + u8 p_bits;
> + u8 t_bits;
> + __le16 n_bits;
> + u8 na_bits;
> + u8 k_bits;
> +} __packed;
> +
> +#define PN_D_FIELD_DLCI GENMASK(5, 0)
> +#define PN_I_CL_FIELD_FTYPE GENMASK(3, 0)
> +#define PN_I_CL_FIELD_ADAPTION GENMASK(7, 4)
> +#define PN_P_FIELD_PRIO GENMASK(5, 0)
> +#define PN_T_FIELD_T1 GENMASK(7, 0)
> +#define PN_N_FIELD_N1 GENMASK(15, 0)
> +#define PN_NA_FIELD_N2 GENMASK(7, 0)
> +#define PN_K_FIELD_K GENMASK(2, 0)
> +
> /* Total number of supported devices */
> #define GSM_TTY_MINORS 256
>
> @@ -411,6 +437,7 @@ static const u8 gsm_fcs8[256] = {
> #define INIT_FCS 0xFF
> #define GOOD_FCS 0xCF
>
> +static void gsm_dlci_close(struct gsm_dlci *dlci);
> static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len);
> static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk);
> static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len,
> @@ -533,6 +560,59 @@ static void gsm_hex_dump_bytes(const char *fname, const u8 *data,
> kfree(prefix);
> }
>
> +/**
> + * gsm_encode_params - encode DLCI parameters
> + * @dlci: DLCI to encode from
> + * @params: buffer to fill with the encoded parameters
> + *
> + * Encodes the parameters according to GSM 07.10 section 5.4.6.3.1
> + * table 3.
> + */
> +static int gsm_encode_params(const struct gsm_dlci *dlci,
> + struct gsm_dlci_param_bits *params)
> +{
> + const struct gsm_mux *gsm = dlci->gsm;
> + unsigned int i, cl;
> +
> + switch (dlci->ftype) {
> + case UIH:
> + i = 0; /* UIH */
> + break;
> + case UI:
> + i = 1; /* UI */
> + break;
> + default:
> + pr_err("%s: unsupported frame type %d\n", __func__,
> + dlci->ftype);
This needs to be dev_err(), right?
And why is it not just dev_dbg()/
> + return -EINVAL;
> + }
> +
> + switch (dlci->adaption) {
> + case 1: /* Unstructured */
> + cl = 0; /* convergence layer type 1 */
> + break;
> + case 2: /* Unstructured with modem bits. */
> + cl = 1; /* convergence layer type 2 */
> + break;
> + default:
> + pr_err("%s: unsupported adaption %d\n", __func__,
> + dlci->adaption);
Again, dev_dbg()?
Do not yet userspace, or external devices, spam kernel logs with
messages.
> + return -EINVAL;
> + }
> +
> + params->d_bits = FIELD_PREP(PN_D_FIELD_DLCI, dlci->addr);
> + /* UIH, convergence layer type 1 */
> + params->i_cl_bits = FIELD_PREP(PN_I_CL_FIELD_FTYPE, i) |
> + FIELD_PREP(PN_I_CL_FIELD_ADAPTION, cl);
> + params->p_bits = FIELD_PREP(PN_P_FIELD_PRIO, dlci->prio);
> + params->t_bits = FIELD_PREP(PN_T_FIELD_T1, gsm->t1);
> + params->n_bits = cpu_to_le16(FIELD_PREP(PN_N_FIELD_N1, dlci->mtu));
> + params->na_bits = FIELD_PREP(PN_NA_FIELD_N2, gsm->n2);
> + params->k_bits = FIELD_PREP(PN_K_FIELD_K, dlci->k);
> +
> + return 0;
> +}
> +
> /**
> * gsm_register_devices - register all tty devices for a given mux index
> *
> @@ -1450,6 +1530,116 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
> dlci->modem_rx = mlines;
> }
>
> +/**
> + * gsm_process_negotiation - process received parameters
> + * @gsm: GSM channel
> + * @addr: DLCI address
> + * @cr: command/response
> + * @params: encoded parameters from the parameter negotiation message
> + *
> + * Used when the response for our parameter negotiation command was
> + * received.
> + */
> +static int gsm_process_negotiation(struct gsm_mux *gsm, unsigned int addr,
> + unsigned int cr,
> + const struct gsm_dlci_param_bits *params)
> +{
> + struct gsm_dlci *dlci = gsm->dlci[addr];
> + unsigned int ftype, i, adaption, prio, n1, k;
> +
> + i = FIELD_GET(PN_I_CL_FIELD_FTYPE, params->i_cl_bits);
> + adaption = FIELD_GET(PN_I_CL_FIELD_ADAPTION, params->i_cl_bits) + 1;
> + prio = FIELD_GET(PN_P_FIELD_PRIO, params->p_bits);
> + n1 = FIELD_GET(PN_N_FIELD_N1, le16_to_cpu(params->n_bits));
> + k = FIELD_GET(PN_K_FIELD_K, params->k_bits);
> +
> + if (n1 < MIN_MTU) {
> + if (debug & DBG_ERRORS)
Please use the proper debug code in the kernel, don't roll your own.
> + pr_info("%s N1 out of range in PN\n", __func__);
This should be dev_dbg().
And never use __func__ in a dev_dbg() call, it's there automatically.
thanks,
greg k-h
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