Please Help me with reading the busy flag of LCD in 4 bit mode

#define data PORTB
#define e PB1
#define rs PB0
#define rw PB2

void lcd_ready() //checks for busy flag
    {

    DDRB&=0b00001111; //data lines as read
    int flag=0;

    cbi(PORTB,rs);
    sbi(PORTB,rw);

    do
        {
        pos_pulse();
        _delay_us(10);
        flag=PINB;
        flag=(flag&0x80); //to store the value of busy flag
        pos_pulse(); //discard lower nibble
        _delay_us(10);
        }while(flag);
       
    DDRB=0xff; //resetting data lines as output
    }

void pos_pulse()
    { 
    cbi(PORTB,e); // eable=0
    _delay_us(2);
    sbi(PORTB,e) ; // eable=1
    _delay_us(2);
    }

void neg_pulse()
    {
    sbi(PORTB,e); // eable=1
    _delay_us(2);
    cbi(PORTB,e) ; // eable=0
    _delay_us(2);
    }

void command(int a) // to receive and send command to LCD
    {
    //higher nibble

    lcd_ready();

    data=(a&0xf0);
    cbi(PORTB,rs); 
    cbi(PORTB,rw);
    neg_pulse();

    //Lower Nibble

    lcd_ready();

    data=((a<<4)&0xf0);
    cbi(PORTB,rs); 
    cbi(PORTB,rw);
    neg_pulse();
    }

void value(int a) //To send Data to the Lcd
    {
    //higher nibble

    lcd_ready();

    data=(a&0xf0);
    sbi(PORTB,rs); 
    cbi(PORTB,rw);
    neg_pulse();

    //Lower Nibble

    lcd_ready();

    data=((a<<4)&0xf0);
    sbi(PORTB,rs); 
    cbi(PORTB,rw);
    neg_pulse();
    }