linux-kernel - Re: [PATCH v5 13/13] tty: gunyah: Add tty console driver for RM Console Services

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Message-ID: <bf9d4365-7750-399f-e488-1611eecca13a@quicinc.com>
Date:   Tue, 11 Oct 2022 15:04:01 -0700
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Jiri Slaby <jirislaby@...nel.org>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        "Will Deacon" <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "Arnd Bergmann" <arnd@...db.de>, <devicetree@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 13/13] tty: gunyah: Add tty console driver for RM
 Console Services



On 10/10/2022 11:02 PM, Jiri Slaby wrote:
> On 11. 10. 22, 2:08, Elliot Berman wrote:
>> Gunyah provides a console for each VM using the VM console resource
>> manager APIs. This driver allows console data from other
>> VMs to be accessed via a TTY device and exports a console device to dump
>> Linux's own logs to our console.
> ...
>> +struct rm_cons_drv_data {
>> +    struct tty_driver *tty_driver;
>> +    struct device *dev;
>> +
>> +    spinlock_t ports_lock;
>> +    struct rm_cons_port *ports[RM_CONS_TTY_ADAPATERS];
>> +
>> +    struct notifier_block rm_cons_notif;
>> +    struct console console;
>> +
>> +    /* below are for printk console.
>> +     * gh_rm_console_* calls will sleep and console_write can be 
>> called from
>> +     * atomic ctx. Two xmit buffers are used. The active buffer is 
>> tracked with
>> +     * co_xmit_idx. Writes go into the co_xmit_buf[co_xmit_idx] buffer.
>> +     * A work is scheduled to flush the bytes. The work will swap the 
>> active buffer
>> +     * and write out the other buffer.
>> +     */
> 
> Ugh, why? This is too ugly and unnecessary. What about passing the kfifo 
> to gh_rm_console_write() instead? You do memcpy() there anyway.
> 

Sure, I can do this instead.